diff --git a/analyzer-baseline.toml b/analyzer-baseline.toml
index 6f5fb0e5..076235f9 100644
--- a/analyzer-baseline.toml
+++ b/analyzer-baseline.toml
@@ -1938,36 +1938,6 @@ code = "less-specific-nested-argument-type"
 message = 'Argument type mismatch for argument #1 of `PhpDb\Sql\Select::columns`: expected `array<array-key, PhpDb\Sql\ExpressionInterface|string>`, but provided type `array<non-negative-int, nonnull>` is less specific.'
 count = 1
 
-[[issues]]
-file = "src/Sql/Combine.php"
-code = "missing-constant-type"
-message = "Class constant `COLUMNS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Combine.php"
-code = "missing-constant-type"
-message = "Class constant `COMBINE_EXCEPT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Combine.php"
-code = "missing-constant-type"
-message = "Class constant `COMBINE_INTERSECT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Combine.php"
-code = "missing-constant-type"
-message = "Class constant `COMBINE_UNION` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Combine.php"
-code = "missing-constant-type"
-message = "Class constant `COMBINE` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Combine.php"
 code = "mixed-assignment"
@@ -2040,54 +2010,6 @@ code = "less-specific-nested-return-statement"
 message = '''Returned type `list{list<mixed>}` is less specific than the declared return type `array{0: list<string>}` for function `PhpDb\Sql\Ddl\AlterTable::processDropIndexes` due to nested 'mixed'.'''
 count = 1
 
-[[issues]]
-file = "src/Sql/Ddl/AlterTable.php"
-code = "missing-constant-type"
-message = "Class constant `ADD_COLUMNS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Ddl/AlterTable.php"
-code = "missing-constant-type"
-message = "Class constant `ADD_CONSTRAINTS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Ddl/AlterTable.php"
-code = "missing-constant-type"
-message = "Class constant `CHANGE_COLUMNS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Ddl/AlterTable.php"
-code = "missing-constant-type"
-message = "Class constant `DROP_COLUMNS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Ddl/AlterTable.php"
-code = "missing-constant-type"
-message = "Class constant `DROP_CONSTRAINTS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Ddl/AlterTable.php"
-code = "missing-constant-type"
-message = "Class constant `DROP_INDEXES` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Ddl/AlterTable.php"
-code = "missing-constant-type"
-message = "Class constant `TABLE_OPTIONS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Ddl/AlterTable.php"
-code = "missing-constant-type"
-message = "Class constant `TABLE` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Ddl/AlterTable.php"
 code = "mixed-assignment"
@@ -2334,30 +2256,6 @@ code = "invalid-return-statement"
 message = '''Invalid return type for function `PhpDb\Sql\Ddl\CreateTable::processTable`: expected `array<array-key, string>`, but found `list{string('')|string('TEMPORARY '), string('')|string('IF NOT EXISTS '), array<array-key, mixed>|null|string}`.'''
 count = 1
 
-[[issues]]
-file = "src/Sql/Ddl/CreateTable.php"
-code = "missing-constant-type"
-message = "Class constant `COLUMNS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Ddl/CreateTable.php"
-code = "missing-constant-type"
-message = "Class constant `CONSTRAINTS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Ddl/CreateTable.php"
-code = "missing-constant-type"
-message = "Class constant `TABLE_OPTIONS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Ddl/CreateTable.php"
-code = "missing-constant-type"
-message = "Class constant `TABLE` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Ddl/CreateTable.php"
 code = "mixed-assignment"
@@ -2406,12 +2304,6 @@ code = "invalid-return-statement"
 message = '''Invalid return type for function `PhpDb\Sql\Ddl\DropTable::processTable`: expected `array<array-key, string>`, but found `list{string('')|string('IF EXISTS '), array<array-key, mixed>|null|string}`.'''
 count = 1
 
-[[issues]]
-file = "src/Sql/Ddl/DropTable.php"
-code = "missing-constant-type"
-message = "Class constant `TABLE` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Ddl/DropTable.php"
 code = "possibly-null-argument"
@@ -2460,18 +2352,6 @@ code = "less-specific-nested-argument-type"
 message = "Argument type mismatch for argument #2 of `str_replace`: expected `array<array-key, string>|string`, but provided type `array<array-key, mixed>|null|string` is less specific."
 count = 1
 
-[[issues]]
-file = "src/Sql/Delete.php"
-code = "missing-constant-type"
-message = "Class constant `SPECIFICATION_DELETE` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Delete.php"
-code = "missing-constant-type"
-message = "Class constant `SPECIFICATION_WHERE` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Delete.php"
 code = "possibly-invalid-argument"
@@ -2532,12 +2412,6 @@ code = "less-specific-nested-argument-type"
 message = 'Argument type mismatch for argument #1 of `PhpDb\Sql\Expression::setParameters`: expected `PhpDb\Sql\ArgumentInterface|PhpDb\Sql\ExpressionInterface|array<array-key, PhpDb\Sql\ArgumentInterface|PhpDb\Sql\ExpressionInterface|list<bool|float|int|null|string>|null|scalar>|list<bool|float|int|null|string>|null|scalar`, but provided type `PhpDb\Sql\ArgumentInterface|PhpDb\Sql\ExpressionInterface|array<array-key, mixed>|list<mixed>|null|scalar` is less specific.'
 count = 1
 
-[[issues]]
-file = "src/Sql/Expression.php"
-code = "missing-constant-type"
-message = "Class constant `PLACEHOLDER` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Expression.php"
 code = "possibly-null-argument"
@@ -2604,30 +2478,6 @@ code = "less-specific-nested-argument-type"
 message = "Argument type mismatch for argument #2 of `implode`: expected `array<array-key, Stringable|null|scalar>|null`, but provided type `list<mixed>` is less specific."
 count = 1
 
-[[issues]]
-file = "src/Sql/Insert.php"
-code = "missing-constant-type"
-message = "Class constant `SPECIFICATION_INSERT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Insert.php"
-code = "missing-constant-type"
-message = "Class constant `SPECIFICATION_SELECT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Insert.php"
-code = "missing-constant-type"
-message = "Class constant `VALUES_MERGE` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Insert.php"
-code = "missing-constant-type"
-message = "Class constant `VALUES_SET` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Insert.php"
 code = "missing-return-type"
@@ -2736,48 +2586,6 @@ code = "invalid-return-statement"
 message = '''Invalid return type for function `PhpDb\Sql\Join::current`: expected `array{'columns': array<array-key, PhpDb\Sql\ExpressionInterface|string>, 'name': PhpDb\Sql\TableIdentifier|non-empty-array<string, PhpDb\Sql\Expression|PhpDb\Sql\Select|PhpDb\Sql\TableIdentifier|string>|string, 'on': PhpDb\Sql\Predicate\PredicateInterface|string, 'type': string}`, but found `array{'columns': array<array-key, PhpDb\Sql\ExpressionInterface|string>, 'name': PhpDb\Sql\TableIdentifier|non-empty-array<string, PhpDb\Sql\Expression|PhpDb\Sql\Select|PhpDb\Sql\TableIdentifier|string>|string, 'on': PhpDb\Sql\Predicate\PredicateInterface|string, 'type': string}|null`.'''
 count = 1
 
-[[issues]]
-file = "src/Sql/Join.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_FULL_OUTER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Join.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_INNER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Join.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_LEFT_OUTER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Join.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_LEFT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Join.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_OUTER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Join.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_RIGHT_OUTER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Join.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_RIGHT` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Join.php"
 code = "nullable-return-statement"
@@ -2970,78 +2778,6 @@ code = "class-must-be-final"
 message = 'Class `PhpDb\Sql\Predicate\Operator` should be declared `final`.'
 count = 1
 
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OPERATOR_EQUAL_TO` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OPERATOR_GREATER_THAN_OR_EQUAL_TO` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OPERATOR_GREATER_THAN` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OPERATOR_LESS_THAN_OR_EQUAL_TO` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OPERATOR_LESS_THAN` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OPERATOR_NOT_EQUAL_TO` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OP_EQ` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OP_GTE` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OP_GT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OP_LTE` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OP_LT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/Operator.php"
-code = "missing-constant-type"
-message = "Class constant `OP_NE` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Predicate/Predicate.php"
 code = "impossible-condition"
@@ -3156,30 +2892,6 @@ code = "less-specific-nested-return-statement"
 message = '''Returned type `array{'spec': non-empty-string, 'values': mixed}` is less specific than the declared return type `array{'spec': string, 'values': list<PhpDb\Sql\ArgumentInterface>}` for function `PhpDb\Sql\Predicate\PredicateSet::getExpressionData` due to nested 'mixed'.'''
 count = 1
 
-[[issues]]
-file = "src/Sql/Predicate/PredicateSet.php"
-code = "missing-constant-type"
-message = "Class constant `COMBINED_BY_AND` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/PredicateSet.php"
-code = "missing-constant-type"
-message = "Class constant `COMBINED_BY_OR` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/PredicateSet.php"
-code = "missing-constant-type"
-message = "Class constant `OP_AND` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Predicate/PredicateSet.php"
-code = "missing-constant-type"
-message = "Class constant `OP_OR` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Predicate/PredicateSet.php"
 code = "mixed-argument"
@@ -3324,168 +3036,6 @@ code = "less-specific-nested-return-statement"
 message = '''Returned type `list{mixed}` is less specific than the declared return type `array{0: string}|null` for function `PhpDb\Sql\Select::processOffset` due to nested 'mixed'.'''
 count = 1
 
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `COLUMNS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `COMBINE_EXCEPT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `COMBINE_INTERSECT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `COMBINE_UNION` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `COMBINE` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `GROUP` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `HAVING` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `JOINS` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_FULL_OUTER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_INNER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_LEFT_OUTER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_LEFT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_OUTER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_RIGHT_OUTER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `JOIN_RIGHT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `LIMIT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `OFFSET` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `ORDER_ASCENDING` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `ORDER_DESCENDING` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `ORDER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `QUANTIFIER_ALL` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `QUANTIFIER_DISTINCT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `QUANTIFIER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `SELECT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `SQL_STAR` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `TABLE` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Select.php"
-code = "missing-constant-type"
-message = "Class constant `WHERE` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Select.php"
 code = "missing-return-type"
@@ -3684,30 +3234,6 @@ code = "missing-api-or-internal"
 message = 'Interface `PhpDb\Sql\SqlInterface` is missing an `@api` or `@internal` annotation.'
 count = 1
 
-[[issues]]
-file = "src/Sql/SqlInterface.php"
-code = "missing-constant-type"
-message = "Class constant `TYPE_IDENTIFIER` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/SqlInterface.php"
-code = "missing-constant-type"
-message = "Class constant `TYPE_LITERAL` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/SqlInterface.php"
-code = "missing-constant-type"
-message = "Class constant `TYPE_SELECT` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/SqlInterface.php"
-code = "missing-constant-type"
-message = "Class constant `TYPE_VALUE` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Update.php"
 code = "class-must-be-final"
@@ -3744,42 +3270,6 @@ code = "less-specific-nested-argument-type"
 message = "Argument type mismatch for argument #2 of `str_replace`: expected `array<array-key, string>|string`, but provided type `array<array-key, mixed>|null|string` is less specific."
 count = 1
 
-[[issues]]
-file = "src/Sql/Update.php"
-code = "missing-constant-type"
-message = "Class constant `SPECIFICATION_JOIN` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Update.php"
-code = "missing-constant-type"
-message = "Class constant `SPECIFICATION_SET` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Update.php"
-code = "missing-constant-type"
-message = "Class constant `SPECIFICATION_UPDATE` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Update.php"
-code = "missing-constant-type"
-message = "Class constant `SPECIFICATION_WHERE` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Update.php"
-code = "missing-constant-type"
-message = "Class constant `VALUES_MERGE` is missing a type hint."
-count = 1
-
-[[issues]]
-file = "src/Sql/Update.php"
-code = "missing-constant-type"
-message = "Class constant `VALUES_SET` is missing a type hint."
-count = 1
-
 [[issues]]
 file = "src/Sql/Update.php"
 code = "missing-return-type"
diff --git a/src/Sql/Combine.php b/src/Sql/Combine.php
index 5053ba64..dd5996c3 100644
--- a/src/Sql/Combine.php
+++ b/src/Sql/Combine.php
@@ -24,15 +24,15 @@
  */
 class Combine extends AbstractPreparableSql
 {
-    final public const COLUMNS = 'columns';
+    final public const string COLUMNS = 'columns';
 
-    final public const COMBINE = 'combine';
+    final public const string COMBINE = 'combine';
 
-    final public const COMBINE_UNION = 'union';
+    final public const string COMBINE_UNION = 'union';
 
-    final public const COMBINE_EXCEPT = 'except';
+    final public const string COMBINE_EXCEPT = 'except';
 
-    final public const COMBINE_INTERSECT = 'intersect';
+    final public const string COMBINE_INTERSECT = 'intersect';
 
     /** @var array<string, Specification> */
     protected array $specifications = [
diff --git a/src/Sql/Ddl/AlterTable.php b/src/Sql/Ddl/AlterTable.php
index 7dae6e5a..47fa6ecd 100644
--- a/src/Sql/Ddl/AlterTable.php
+++ b/src/Sql/Ddl/AlterTable.php
@@ -19,21 +19,21 @@
  */
 class AlterTable extends AbstractSql
 {
-    final public const ADD_COLUMNS = 'addColumns';
+    final public const string ADD_COLUMNS = 'addColumns';
 
-    final public const ADD_CONSTRAINTS = 'addConstraints';
+    final public const string ADD_CONSTRAINTS = 'addConstraints';
 
-    final public const CHANGE_COLUMNS = 'changeColumns';
+    final public const string CHANGE_COLUMNS = 'changeColumns';
 
-    final public const DROP_COLUMNS = 'dropColumns';
+    final public const string DROP_COLUMNS = 'dropColumns';
 
-    final public const DROP_CONSTRAINTS = 'dropConstraints';
+    final public const string DROP_CONSTRAINTS = 'dropConstraints';
 
-    final public const DROP_INDEXES = 'dropIndexes';
+    final public const string DROP_INDEXES = 'dropIndexes';
 
-    final public const TABLE = 'table';
+    final public const string TABLE = 'table';
 
-    final public const TABLE_OPTIONS = 'tableOptions';
+    final public const string TABLE_OPTIONS = 'tableOptions';
 
     /** @var list<Column\ColumnInterface> */
     protected array $addColumns = [];
diff --git a/src/Sql/Ddl/CreateTable.php b/src/Sql/Ddl/CreateTable.php
index ac5fc91b..28b519a4 100644
--- a/src/Sql/Ddl/CreateTable.php
+++ b/src/Sql/Ddl/CreateTable.php
@@ -20,13 +20,13 @@
  */
 class CreateTable extends AbstractSql
 {
-    final public const COLUMNS = 'columns';
+    final public const string COLUMNS = 'columns';
 
-    final public const CONSTRAINTS = 'constraints';
+    final public const string CONSTRAINTS = 'constraints';
 
-    final public const TABLE = 'table';
+    final public const string TABLE = 'table';
 
-    final public const TABLE_OPTIONS = 'tableOptions';
+    final public const string TABLE_OPTIONS = 'tableOptions';
 
     /** @var list<Column\ColumnInterface> */
     protected array $columns = [];
diff --git a/src/Sql/Ddl/DropTable.php b/src/Sql/Ddl/DropTable.php
index 4bd314b5..9bdd5bfa 100644
--- a/src/Sql/Ddl/DropTable.php
+++ b/src/Sql/Ddl/DropTable.php
@@ -13,7 +13,7 @@
  */
 class DropTable extends AbstractSql
 {
-    final public const TABLE = 'table';
+    final public const string TABLE = 'table';
 
     protected bool $ifExists = false;
 
diff --git a/src/Sql/Delete.php b/src/Sql/Delete.php
index 20fb69f1..1a621dbc 100644
--- a/src/Sql/Delete.php
+++ b/src/Sql/Delete.php
@@ -23,9 +23,9 @@ class Delete extends AbstractPreparableSql
     /**@#+
      * @const
      */
-    public const SPECIFICATION_DELETE = 'delete';
+    public const string SPECIFICATION_DELETE = 'delete';
 
-    final public const SPECIFICATION_WHERE = 'where';
+    final public const string SPECIFICATION_WHERE = 'where';
 
     /** @#- */
 
diff --git a/src/Sql/Expression.php b/src/Sql/Expression.php
index 1bc313ef..5820bcb1 100644
--- a/src/Sql/Expression.php
+++ b/src/Sql/Expression.php
@@ -26,7 +26,7 @@ class Expression extends AbstractExpression
     /**
      * @const
      */
-    final public const PLACEHOLDER = '?';
+    final public const string PLACEHOLDER = '?';
 
     protected string $expression = '';
 
diff --git a/src/Sql/Insert.php b/src/Sql/Insert.php
index 52fb1a70..2ba0ba71 100644
--- a/src/Sql/Insert.php
+++ b/src/Sql/Insert.php
@@ -31,13 +31,13 @@ class Insert extends AbstractPreparableSql
      *
      * @const
      */
-    public const SPECIFICATION_INSERT = 'insert';
+    public const string SPECIFICATION_INSERT = 'insert';
 
-    final public const SPECIFICATION_SELECT = 'select';
+    final public const string SPECIFICATION_SELECT = 'select';
 
-    final public const VALUES_MERGE = 'merge';
+    final public const string VALUES_MERGE = 'merge';
 
-    final public const VALUES_SET = 'set';
+    final public const string VALUES_SET = 'set';
 
     /** @var array<string, Specification> */
     protected array $specifications = [
diff --git a/src/Sql/Join.php b/src/Sql/Join.php
index 4dcbb46f..9f619e01 100644
--- a/src/Sql/Join.php
+++ b/src/Sql/Join.php
@@ -38,19 +38,19 @@
  */
 class Join implements Iterator, Countable
 {
-    final public const JOIN_INNER = 'inner';
+    final public const string JOIN_INNER = 'inner';
 
-    final public const JOIN_OUTER = 'outer';
+    final public const string JOIN_OUTER = 'outer';
 
-    final public const JOIN_FULL_OUTER = 'full outer';
+    final public const string JOIN_FULL_OUTER = 'full outer';
 
-    final public const JOIN_LEFT = 'left';
+    final public const string JOIN_LEFT = 'left';
 
-    final public const JOIN_RIGHT = 'right';
+    final public const string JOIN_RIGHT = 'right';
 
-    final public const JOIN_RIGHT_OUTER = 'right outer';
+    final public const string JOIN_RIGHT_OUTER = 'right outer';
 
-    final public const JOIN_LEFT_OUTER = 'left outer';
+    final public const string JOIN_LEFT_OUTER = 'left outer';
 
     /**
      * Current iterator position.
diff --git a/src/Sql/Predicate/Operator.php b/src/Sql/Predicate/Operator.php
index 379c0e45..4d98e855 100644
--- a/src/Sql/Predicate/Operator.php
+++ b/src/Sql/Predicate/Operator.php
@@ -16,29 +16,29 @@
 
 class Operator extends AbstractExpression implements PredicateInterface
 {
-    final public const OPERATOR_EQUAL_TO = '=';
+    final public const string OPERATOR_EQUAL_TO = '=';
 
-    final public const OP_EQ = '=';
+    final public const string OP_EQ = '=';
 
-    final public const OPERATOR_NOT_EQUAL_TO = '!=';
+    final public const string OPERATOR_NOT_EQUAL_TO = '!=';
 
-    final public const OP_NE = '!=';
+    final public const string OP_NE = '!=';
 
-    final public const OPERATOR_LESS_THAN = '<';
+    final public const string OPERATOR_LESS_THAN = '<';
 
-    final public const OP_LT = '<';
+    final public const string OP_LT = '<';
 
-    final public const OPERATOR_LESS_THAN_OR_EQUAL_TO = '<=';
+    final public const string OPERATOR_LESS_THAN_OR_EQUAL_TO = '<=';
 
-    final public const OP_LTE = '<=';
+    final public const string OP_LTE = '<=';
 
-    final public const OPERATOR_GREATER_THAN = '>';
+    final public const string OPERATOR_GREATER_THAN = '>';
 
-    final public const OP_GT = '>';
+    final public const string OP_GT = '>';
 
-    final public const OPERATOR_GREATER_THAN_OR_EQUAL_TO = '>=';
+    final public const string OPERATOR_GREATER_THAN_OR_EQUAL_TO = '>=';
 
-    final public const OP_GTE = '>=';
+    final public const string OP_GTE = '>=';
 
     protected ?ArgumentInterface $left     = null;
     protected ?ArgumentInterface $right    = null;
diff --git a/src/Sql/Predicate/PredicateSet.php b/src/Sql/Predicate/PredicateSet.php
index c4e015a9..96f6bc06 100644
--- a/src/Sql/Predicate/PredicateSet.php
+++ b/src/Sql/Predicate/PredicateSet.php
@@ -21,15 +21,15 @@
 
 class PredicateSet implements PredicateInterface, Countable
 {
-    final public const OP_AND = 'AND';
+    final public const string OP_AND = 'AND';
 
-    final public const OP_OR = 'OR';
+    final public const string OP_OR = 'OR';
 
     /** @deprecated Use OP_AND instead */
-    final public const COMBINED_BY_AND = self::OP_AND;
+    final public const string COMBINED_BY_AND = self::OP_AND;
 
     /** @deprecated Use OP_OR instead */
-    final public const COMBINED_BY_OR = self::OP_OR;
+    final public const string COMBINED_BY_OR = self::OP_OR;
 
     protected string $defaultCombination = self::OP_AND;
 
diff --git a/src/Sql/Select.php b/src/Sql/Select.php
index dbde02f5..58cfdfa0 100644
--- a/src/Sql/Select.php
+++ b/src/Sql/Select.php
@@ -48,59 +48,59 @@ class Select extends AbstractPreparableSql
      *
      * @const
      */
-    final public const SELECT = 'select';
+    final public const string SELECT = 'select';
 
-    final public const QUANTIFIER = 'quantifier';
+    final public const string QUANTIFIER = 'quantifier';
 
-    final public const COLUMNS = 'columns';
+    final public const string COLUMNS = 'columns';
 
-    final public const TABLE = 'table';
+    final public const string TABLE = 'table';
 
-    final public const JOINS = 'joins';
+    final public const string JOINS = 'joins';
 
-    final public const WHERE = 'where';
+    final public const string WHERE = 'where';
 
-    final public const GROUP = 'group';
+    final public const string GROUP = 'group';
 
-    final public const HAVING = 'having';
+    final public const string HAVING = 'having';
 
-    final public const ORDER = 'order';
+    final public const string ORDER = 'order';
 
-    final public const LIMIT = 'limit';
+    final public const string LIMIT = 'limit';
 
-    final public const OFFSET = 'offset';
+    final public const string OFFSET = 'offset';
 
-    final public const QUANTIFIER_DISTINCT = 'DISTINCT';
+    final public const string QUANTIFIER_DISTINCT = 'DISTINCT';
 
-    final public const QUANTIFIER_ALL = 'ALL';
+    final public const string QUANTIFIER_ALL = 'ALL';
 
-    final public const JOIN_INNER = Join::JOIN_INNER;
+    final public const string JOIN_INNER = Join::JOIN_INNER;
 
-    final public const JOIN_OUTER = Join::JOIN_OUTER;
+    final public const string JOIN_OUTER = Join::JOIN_OUTER;
 
-    final public const JOIN_FULL_OUTER = Join::JOIN_FULL_OUTER;
+    final public const string JOIN_FULL_OUTER = Join::JOIN_FULL_OUTER;
 
-    final public const JOIN_LEFT = Join::JOIN_LEFT;
+    final public const string JOIN_LEFT = Join::JOIN_LEFT;
 
-    final public const JOIN_RIGHT = Join::JOIN_RIGHT;
+    final public const string JOIN_RIGHT = Join::JOIN_RIGHT;
 
-    final public const JOIN_RIGHT_OUTER = Join::JOIN_RIGHT_OUTER;
+    final public const string JOIN_RIGHT_OUTER = Join::JOIN_RIGHT_OUTER;
 
-    final public const JOIN_LEFT_OUTER = Join::JOIN_LEFT_OUTER;
+    final public const string JOIN_LEFT_OUTER = Join::JOIN_LEFT_OUTER;
 
-    final public const SQL_STAR = '*';
+    final public const string SQL_STAR = '*';
 
-    final public const ORDER_ASCENDING = 'ASC';
+    final public const string ORDER_ASCENDING = 'ASC';
 
-    final public const ORDER_DESCENDING = 'DESC';
+    final public const string ORDER_DESCENDING = 'DESC';
 
-    final public const COMBINE = 'combine';
+    final public const string COMBINE = 'combine';
 
-    final public const COMBINE_UNION = 'union';
+    final public const string COMBINE_UNION = 'union';
 
-    final public const COMBINE_EXCEPT = 'except';
+    final public const string COMBINE_EXCEPT = 'except';
 
-    final public const COMBINE_INTERSECT = 'intersect';
+    final public const string COMBINE_INTERSECT = 'intersect';
 
     /** @var array<string, Specification> */
     protected array $specifications = [
diff --git a/src/Sql/SqlInterface.php b/src/Sql/SqlInterface.php
index 8f2a93ec..e1e4b94b 100644
--- a/src/Sql/SqlInterface.php
+++ b/src/Sql/SqlInterface.php
@@ -15,13 +15,13 @@ interface SqlInterface
      *
      * @see ArgumentType
      */
-    public const TYPE_IDENTIFIER = 'identifier';
+    public const string TYPE_IDENTIFIER = 'identifier';
 
-    public const TYPE_VALUE = 'value';
+    public const string TYPE_VALUE = 'value';
 
-    public const TYPE_LITERAL = 'literal';
+    public const string TYPE_LITERAL = 'literal';
 
-    public const TYPE_SELECT = 'select';
+    public const string TYPE_SELECT = 'select';
 
     /**
      * Get SQL string for statement
diff --git a/src/Sql/Update.php b/src/Sql/Update.php
index fe6db09d..a17e9725 100644
--- a/src/Sql/Update.php
+++ b/src/Sql/Update.php
@@ -30,17 +30,17 @@ class Update extends AbstractPreparableSql
     /**@#++
      * @const
      */
-    public const SPECIFICATION_UPDATE = 'update';
+    public const string SPECIFICATION_UPDATE = 'update';
 
-    final public const SPECIFICATION_SET = 'set';
+    final public const string SPECIFICATION_SET = 'set';
 
-    final public const SPECIFICATION_WHERE = 'where';
+    final public const string SPECIFICATION_WHERE = 'where';
 
-    final public const SPECIFICATION_JOIN = 'joins';
+    final public const string SPECIFICATION_JOIN = 'joins';
 
-    final public const VALUES_MERGE = 'merge';
+    final public const string VALUES_MERGE = 'merge';
 
-    final public const VALUES_SET = 'set';
+    final public const string VALUES_SET = 'set';
 
     /** @#-* */
 
diff --git a/test/unit/TestAsset/DeleteIgnore.php b/test/unit/TestAsset/DeleteIgnore.php
index f18dbfc1..65592ec2 100644
--- a/test/unit/TestAsset/DeleteIgnore.php
+++ b/test/unit/TestAsset/DeleteIgnore.php
@@ -11,7 +11,7 @@
 
 class DeleteIgnore extends Delete
 {
-    public const SPECIFICATION_DELETE = 'deleteIgnore';
+    public const string SPECIFICATION_DELETE = 'deleteIgnore';
 
     /** @var array<string, string> */
     protected array $specifications = [
diff --git a/test/unit/TestAsset/Replace.php b/test/unit/TestAsset/Replace.php
index 0097f1ef..e12e6984 100644
--- a/test/unit/TestAsset/Replace.php
+++ b/test/unit/TestAsset/Replace.php
@@ -11,7 +11,7 @@
 
 class Replace extends Insert
 {
-    public const SPECIFICATION_INSERT = 'replace';
+    public const string SPECIFICATION_INSERT = 'replace';
 
     /** @var array<string, string> */
     protected array $specifications = [
diff --git a/test/unit/TestAsset/UpdateIgnore.php b/test/unit/TestAsset/UpdateIgnore.php
index 0f2ca17d..9073b102 100644
--- a/test/unit/TestAsset/UpdateIgnore.php
+++ b/test/unit/TestAsset/UpdateIgnore.php
@@ -19,7 +19,7 @@ class UpdateIgnore extends Update
      *
      * @psalm-suppress InvalidClassConstantType
      */
-    public const SPECIFICATION_UPDATE = 'updateIgnore';
+    public const string SPECIFICATION_UPDATE = 'updateIgnore';
 
     /** @var array<string, string> */
     protected array $specifications = [