diff --git a/CHANGELOG.md b/CHANGELOG.md
index 113b61433..bdae0719c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -45,6 +45,7 @@
 - Enh #885: Refactor `AbstractDsn` class (@Tigrov)
 - Chg #889: Update `AbstractDMLQueryBuilder::insertBatch()` method (@Tigrov)
 - Enh #890: Add properties of `AbstractColumnSchema` class to constructor (@Tigrov)
+- New #899: Add `ColumnSchemaInterface::hasDefaultValue()` and `ColumnSchemaInterface::null()` methods (@Tigrov)
 
 ## 1.3.0 March 21, 2024
 
diff --git a/UPGRADE.md b/UPGRADE.md
index a22e6df49..2b6379bbc 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -72,9 +72,11 @@ and the following changes were made:
 - `reference(ForeignKeyConstraint|null $reference)` method is added;
 - `getReference()` method is added;
 - `notNull(bool $notNull = true)` method is added;
+- `null()` method is added;
 - `isNotNull()` method is added;
 - `unique(bool $unique = true)` method is added;
 - `isUnique()` method is added;
+- `hasDefaultValue()` method is added;
 - all `AbstractColumnSchema` class properties except `$type` moved to constructor;
 - added `DEFAULT_TYPE` constant to `AbstractColumnSchema` class;
 - added method chaining.
diff --git a/src/QueryBuilder/AbstractColumnDefinitionBuilder.php b/src/QueryBuilder/AbstractColumnDefinitionBuilder.php
index 6682de87d..ac08b2032 100644
--- a/src/QueryBuilder/AbstractColumnDefinitionBuilder.php
+++ b/src/QueryBuilder/AbstractColumnDefinitionBuilder.php
@@ -126,7 +126,7 @@ protected function buildDefault(ColumnSchemaInterface $column): string
         }
 
         if ($column->isAutoIncrement() && $column->getType() !== ColumnType::UUID
-            || $column->getDefaultValue() === null
+            || !$column->hasDefaultValue()
         ) {
             return '';
         }
@@ -149,19 +149,15 @@ protected function buildDefaultValue(ColumnSchemaInterface $column): string|null
     {
         $value = $column->dbTypecast($column->getDefaultValue());
 
-        if ($value === null) {
-            return null;
-        }
-
-        if ($value instanceof ExpressionInterface) {
-            return $this->queryBuilder->buildExpression($value);
-        }
-
         /** @var string */
         return match (gettype($value)) {
             GettypeResult::INTEGER => (string) $value,
             GettypeResult::DOUBLE => (string) $value,
             GettypeResult::BOOLEAN => $value ? 'TRUE' : 'FALSE',
+            GettypeResult::NULL => $column->isNotNull() !== true ? 'NULL' : null,
+            GettypeResult::OBJECT => $value instanceof ExpressionInterface
+                ? $this->queryBuilder->buildExpression($value)
+                : $this->queryBuilder->quoter()->quoteValue((string) $value),
             default => $this->queryBuilder->quoter()->quoteValue((string) $value),
         };
     }
@@ -186,7 +182,11 @@ protected function buildExtra(ColumnSchemaInterface $column): string
      */
     protected function buildNotNull(ColumnSchemaInterface $column): string
     {
-        return $column->isNotNull() ? ' NOT NULL' : '';
+        return match ($column->isNotNull()) {
+            true => ' NOT NULL',
+            false => ' NULL',
+            default => '',
+        };
     }
 
     /**
diff --git a/src/Schema/Column/AbstractColumnSchema.php b/src/Schema/Column/AbstractColumnSchema.php
index 377d0f952..626063a36 100644
--- a/src/Schema/Column/AbstractColumnSchema.php
+++ b/src/Schema/Column/AbstractColumnSchema.php
@@ -6,9 +6,9 @@
 
 use Yiisoft\Db\Constant\ColumnType;
 use Yiisoft\Db\Constant\PhpType;
-
 use Yiisoft\Db\Constraint\ForeignKeyConstraint;
 
+use function array_key_exists;
 use function property_exists;
 
 /**
@@ -43,6 +43,11 @@ abstract class AbstractColumnSchema implements ColumnSchemaInterface
      */
     protected const DEFAULT_TYPE = ColumnType::STRING;
 
+    /**
+     * @var mixed $defaultValue The default value of the column.
+     */
+    private mixed $defaultValue;
+
     /**
      * @var string The column abstract type
      * @psalm-var ColumnType::*
@@ -56,12 +61,11 @@ abstract class AbstractColumnSchema implements ColumnSchemaInterface
      * @param string|null $comment The column's comment.
      * @param bool $computed Whether the column is a computed column.
      * @param string|null $dbType The column's database type.
-     * @param mixed $defaultValue The default value of the column.
      * @param array|null $enumValues The list of possible values for an ENUM column.
      * @param string|null $extra Any extra information that needs to be appended to the column's definition.
      * @param bool $primaryKey Whether the column is a primary key.
      * @param string|null $name The column's name.
-     * @param bool $notNull Whether the column is not nullable.
+     * @param bool|null $notNull Whether the column is not nullable.
      * @param ForeignKeyConstraint|null $reference The foreign key constraint.
      * @param int|null $scale The number of digits to the right of the decimal point.
      * @param int|null $size The column's size.
@@ -79,12 +83,11 @@ public function __construct(
         private string|null $comment = null,
         private bool $computed = false,
         private string|null $dbType = null,
-        private mixed $defaultValue = null,
         private array|null $enumValues = null,
         private string|null $extra = null,
         private bool $primaryKey = false,
         private string|null $name = null,
-        private bool $notNull = false,
+        private bool|null $notNull = null,
         private ForeignKeyConstraint|null $reference = null,
         private int|null $scale = null,
         private int|null $size = null,
@@ -94,6 +97,11 @@ public function __construct(
     ) {
         $this->type = $type ?? static::DEFAULT_TYPE;
 
+        if (array_key_exists('defaultValue', $args)) {
+            $this->defaultValue = $args['defaultValue'];
+            unset($args['defaultValue']);
+        }
+
         /** @var array<string, mixed> $args */
         foreach ($args as $property => $value) {
             if (property_exists($this, $property)) {
@@ -159,31 +167,37 @@ public function extra(string|null $extra): static
         return $this;
     }
 
+    /** @psalm-mutation-free */
     public function getCheck(): string|null
     {
         return $this->check;
     }
 
+    /** @psalm-mutation-free */
     public function getComment(): string|null
     {
         return $this->comment;
     }
 
+    /** @psalm-mutation-free */
     public function getDbType(): string|null
     {
         return $this->dbType;
     }
 
+    /** @psalm-mutation-free */
     public function getDefaultValue(): mixed
     {
-        return $this->defaultValue;
+        return $this->defaultValue ?? null;
     }
 
+    /** @psalm-mutation-free */
     public function getEnumValues(): array|null
     {
         return $this->enumValues;
     }
 
+    /** @psalm-mutation-free */
     public function getExtra(): string|null
     {
         return $this->extra;
@@ -191,6 +205,7 @@ public function getExtra(): string|null
 
     /**
      * @deprecated Will be removed in version 2.0.
+     * @psalm-mutation-free
      */
     public function getName(): string|null
     {
@@ -199,70 +214,89 @@ public function getName(): string|null
 
     /**
      * @deprecated Use {@see getSize()} instead. Will be removed in version 2.0.
+     * @psalm-mutation-free
      */
     public function getPrecision(): int|null
     {
         return $this->getSize();
     }
 
+    /** @psalm-mutation-free */
     public function getPhpType(): string
     {
         return PhpType::MIXED;
     }
 
+    /** @psalm-mutation-free */
     public function getReference(): ForeignKeyConstraint|null
     {
         return $this->reference;
     }
 
+    /** @psalm-mutation-free */
     public function getScale(): int|null
     {
         return $this->scale;
     }
 
+    /** @psalm-mutation-free */
     public function getSize(): int|null
     {
         return $this->size;
     }
 
+    /** @psalm-mutation-free */
     public function getType(): string
     {
         return $this->type;
     }
 
+    /** @psalm-mutation-free */
+    public function hasDefaultValue(): bool
+    {
+        return property_exists($this, 'defaultValue');
+    }
+
     /**
      * @deprecated Use {@see isNotNull()} instead. Will be removed in version 2.0.
+     * @psalm-mutation-free
      */
     public function isAllowNull(): bool
     {
         return !$this->isNotNull();
     }
 
+    /** @psalm-mutation-free */
     public function isAutoIncrement(): bool
     {
         return $this->autoIncrement;
     }
 
+    /** @psalm-mutation-free */
     public function isComputed(): bool
     {
         return $this->computed;
     }
 
-    public function isNotNull(): bool
+    /** @psalm-mutation-free */
+    public function isNotNull(): bool|null
     {
         return $this->notNull;
     }
 
+    /** @psalm-mutation-free */
     public function isPrimaryKey(): bool
     {
         return $this->primaryKey;
     }
 
+    /** @psalm-mutation-free */
     public function isUnique(): bool
     {
         return $this->unique;
     }
 
+    /** @psalm-mutation-free */
     public function isUnsigned(): bool
     {
         return $this->unsigned;
@@ -277,12 +311,18 @@ public function name(string|null $name): static
         return $this;
     }
 
-    public function notNull(bool $notNull = true): static
+    public function notNull(bool|null $notNull = true): static
     {
         $this->notNull = $notNull;
         return $this;
     }
 
+    public function null(): static
+    {
+        $this->notNull = false;
+        return $this;
+    }
+
     /**
      * @deprecated Use {@see size()} instead. Will be removed in version 2.0.
      */
diff --git a/src/Schema/Column/ArrayColumnSchema.php b/src/Schema/Column/ArrayColumnSchema.php
index 7f60ea92f..0d3e24149 100644
--- a/src/Schema/Column/ArrayColumnSchema.php
+++ b/src/Schema/Column/ArrayColumnSchema.php
@@ -85,12 +85,14 @@ public function dimension(int $dimension): static
      * @return int the dimension of the array.
      *
      * @psalm-return positive-int
+     * @psalm-mutation-free
      */
     public function getDimension(): int
     {
         return $this->dimension;
     }
 
+    /** @psalm-mutation-free */
     public function getPhpType(): string
     {
         return PhpType::ARRAY;
diff --git a/src/Schema/Column/BigIntColumnSchema.php b/src/Schema/Column/BigIntColumnSchema.php
index 30e0b6227..b082f2f83 100644
--- a/src/Schema/Column/BigIntColumnSchema.php
+++ b/src/Schema/Column/BigIntColumnSchema.php
@@ -41,6 +41,7 @@ public function dbTypecast(mixed $value): int|string|ExpressionInterface|null
         };
     }
 
+    /** @psalm-mutation-free */
     public function getPhpType(): string
     {
         return PhpType::STRING;
diff --git a/src/Schema/Column/BitColumnSchema.php b/src/Schema/Column/BitColumnSchema.php
index a2cdc30d7..9979afbac 100644
--- a/src/Schema/Column/BitColumnSchema.php
+++ b/src/Schema/Column/BitColumnSchema.php
@@ -27,6 +27,7 @@ public function dbTypecast(mixed $value): int|string|ExpressionInterface|null
         };
     }
 
+    /** @psalm-mutation-free */
     public function getPhpType(): string
     {
         return PhpType::INT;
diff --git a/src/Schema/Column/BooleanColumnSchema.php b/src/Schema/Column/BooleanColumnSchema.php
index 4d60ba2dd..c20e4484f 100644
--- a/src/Schema/Column/BooleanColumnSchema.php
+++ b/src/Schema/Column/BooleanColumnSchema.php
@@ -25,6 +25,7 @@ public function dbTypecast(mixed $value): bool|ExpressionInterface|null
         };
     }
 
+    /** @psalm-mutation-free */
     public function getPhpType(): string
     {
         return PhpType::BOOL;
diff --git a/src/Schema/Column/ColumnSchemaInterface.php b/src/Schema/Column/ColumnSchemaInterface.php
index ffaf24330..22843e824 100644
--- a/src/Schema/Column/ColumnSchemaInterface.php
+++ b/src/Schema/Column/ColumnSchemaInterface.php
@@ -148,13 +148,15 @@ public function extra(string|null $extra): static;
      * Returns the check constraint for the column.
      *
      * @see check()
- */
+     * @psalm-mutation-free
+    */
     public function getCheck(): string|null;
 
     /**
      * @return string|null The comment of the column.
      *
      * @see comment()
+     * @psalm-mutation-free
      */
     public function getComment(): string|null;
 
@@ -166,6 +168,7 @@ public function getComment(): string|null;
      * separately via {@see getSize()}.
      *
      * @see dbType()
+     * @psalm-mutation-free
      */
     public function getDbType(): string|null;
 
@@ -173,6 +176,7 @@ public function getDbType(): string|null;
      * @return mixed The default value of the column.
      *
      * @see defaultValue()
+     * @psalm-mutation-free
      */
     public function getDefaultValue(): mixed;
 
@@ -180,6 +184,7 @@ public function getDefaultValue(): mixed;
      * @return array|null The enum values of the column.
      *
      * @see enumValues()
+     * @psalm-mutation-free
      */
     public function getEnumValues(): array|null;
 
@@ -187,6 +192,7 @@ public function getEnumValues(): array|null;
      * @return string|null The extra SQL for the column.
      *
      * @see extra()
+     * @psalm-mutation-free
      */
     public function getExtra(): string|null;
 
@@ -194,6 +200,7 @@ public function getExtra(): string|null;
      * @return string|null The name of the column.
      *
      * @deprecated Will be removed in version 2.0.
+     * @psalm-mutation-free
      */
     public function getName(): string|null;
 
@@ -203,6 +210,7 @@ public function getName(): string|null;
      * @see precision()
      *
      * @deprecated Use {@see getSize()} instead. Will be removed in version 2.0.
+     * @psalm-mutation-free
      */
     public function getPrecision(): int|null;
 
@@ -211,6 +219,7 @@ public function getPrecision(): int|null;
      *
      * @return string The PHP type of the column.
      * @psalm-return PhpType::*
+     * @psalm-mutation-free
      */
     public function getPhpType(): string;
 
@@ -218,6 +227,7 @@ public function getPhpType(): string;
      * Returns the reference to the foreign key constraint.
      *
      * @see reference()
+     * @psalm-mutation-free
      */
     public function getReference(): ForeignKeyConstraint|null;
 
@@ -225,6 +235,7 @@ public function getReference(): ForeignKeyConstraint|null;
      * @return int|null The scale of the column.
      *
      * @see scale()
+     * @psalm-mutation-free
      */
     public function getScale(): int|null;
 
@@ -232,6 +243,7 @@ public function getScale(): int|null;
      * @return int|null The size of the column.
      *
      * @see size()
+     * @psalm-mutation-free
      */
     public function getSize(): int|null;
 
@@ -240,15 +252,20 @@ public function getSize(): int|null;
      * @psalm-return ColumnType::*
      *
      * @see type()
+     * @psalm-mutation-free
      */
     public function getType(): string;
 
+    /** @psalm-mutation-free */
+    public function hasDefaultValue(): bool;
+
     /**
      * Whether this column is nullable.
      *
      * @see allowNull()
      *
      * @deprecated Use {@see isNotNull()} instead. Will be removed in version 2.0.
+     * @psalm-mutation-free
      */
     public function isAllowNull(): bool;
 
@@ -258,6 +275,7 @@ public function isAllowNull(): bool;
      * This is only meaningful when {@see type} is `smallint`, `integer` or `bigint`.
      *
      * @see autoIncrement()
+     * @psalm-mutation-free
      */
     public function isAutoIncrement(): bool;
 
@@ -265,6 +283,7 @@ public function isAutoIncrement(): bool;
      * Whether this column is computed.
      *
      * @see computed()
+     * @psalm-mutation-free
      */
     public function isComputed(): bool;
 
@@ -272,13 +291,15 @@ public function isComputed(): bool;
      * Whether this column is not nullable.
      *
      * @see notNull()
+     * @psalm-mutation-free
      */
-    public function isNotNull(): bool;
+    public function isNotNull(): bool|null;
 
     /**
      * Whether this column is a part of primary key.
      *
      * @see primaryKey()
+     * @psalm-mutation-free
      */
     public function isPrimaryKey(): bool;
 
@@ -286,6 +307,7 @@ public function isPrimaryKey(): bool;
      * Whether this column has a unique index.
      *
      * @see unique()
+     * @psalm-mutation-free
      */
     public function isUnique(): bool;
 
@@ -294,6 +316,7 @@ public function isUnique(): bool;
      * or `bigint`.
      *
      * @see unsigned()
+     * @psalm-mutation-free
      */
     public function isUnsigned(): bool;
 
@@ -321,6 +344,11 @@ public function name(string|null $name): static;
      */
     public function notNull(bool $notNull = true): static;
 
+    /**
+     * Whether the column is nullable. Alias of {@see notNull(false)}.
+     */
+    public function null(): static;
+
     /**
      * Converts the input value according to {@see phpType} after retrieval from the database.
      *
diff --git a/src/Schema/Column/DoubleColumnSchema.php b/src/Schema/Column/DoubleColumnSchema.php
index 674e2abb0..932b5294a 100644
--- a/src/Schema/Column/DoubleColumnSchema.php
+++ b/src/Schema/Column/DoubleColumnSchema.php
@@ -29,6 +29,7 @@ public function dbTypecast(mixed $value): float|ExpressionInterface|null
         };
     }
 
+    /** @psalm-mutation-free */
     public function getPhpType(): string
     {
         return PhpType::FLOAT;
diff --git a/src/Schema/Column/IntegerColumnSchema.php b/src/Schema/Column/IntegerColumnSchema.php
index 30513ed80..e4710452a 100644
--- a/src/Schema/Column/IntegerColumnSchema.php
+++ b/src/Schema/Column/IntegerColumnSchema.php
@@ -29,6 +29,7 @@ public function dbTypecast(mixed $value): int|ExpressionInterface|null
         };
     }
 
+    /** @psalm-mutation-free */
     public function getPhpType(): string
     {
         return PhpType::INT;
diff --git a/src/Schema/Column/StringColumnSchema.php b/src/Schema/Column/StringColumnSchema.php
index 992abe7de..855bc3bd0 100644
--- a/src/Schema/Column/StringColumnSchema.php
+++ b/src/Schema/Column/StringColumnSchema.php
@@ -29,6 +29,7 @@ public function dbTypecast(mixed $value): mixed
         };
     }
 
+    /** @psalm-mutation-free */
     public function getPhpType(): string
     {
         return PhpType::STRING;
diff --git a/src/Schema/Column/StructuredColumnSchema.php b/src/Schema/Column/StructuredColumnSchema.php
index d71315d41..be08a0b27 100644
--- a/src/Schema/Column/StructuredColumnSchema.php
+++ b/src/Schema/Column/StructuredColumnSchema.php
@@ -52,12 +52,14 @@ public function columns(array $columns): static
      * Get the metadata of the structured type columns.
      *
      * @return ColumnSchemaInterface[]
+     * @psalm-mutation-free
      */
     public function getColumns(): array
     {
         return $this->columns;
     }
 
+    /** @psalm-mutation-free */
     public function getPhpType(): string
     {
         return PhpType::ARRAY;
diff --git a/tests/Db/Schema/ColumnSchemaTest.php b/tests/Db/Schema/ColumnSchemaTest.php
index 3f1539653..591f1bc8c 100644
--- a/tests/Db/Schema/ColumnSchemaTest.php
+++ b/tests/Db/Schema/ColumnSchemaTest.php
@@ -120,12 +120,15 @@ public function testDefaultValue(): void
     {
         $column = new ColumnSchema();
 
+        $this->assertFalse($column->hasDefaultValue());
         $this->assertNull($column->getDefaultValue());
         $this->assertSame($column, $column->defaultValue('test'));
+        $this->assertTrue($column->hasDefaultValue());
         $this->assertSame('test', $column->getDefaultValue());
 
         $column->defaultValue(null);
 
+        $this->assertTrue($column->hasDefaultValue());
         $this->assertNull($column->getDefaultValue());
     }
 
@@ -180,7 +183,7 @@ public function testNotNull(): void
     {
         $column = new ColumnSchema();
 
-        $this->assertFalse($column->isNotNull());
+        $this->assertNull($column->isNotNull());
         $this->assertSame($column, $column->notNull());
         $this->assertTrue($column->isNotNull());
 
@@ -188,9 +191,13 @@ public function testNotNull(): void
 
         $this->assertFalse($column->isNotNull());
 
-        $column->notNull(true);
+        $column->notNull(null);
 
-        $this->assertTrue($column->isNotNull());
+        $this->assertNull($column->isNotNull());
+
+        $column->null();
+
+        $this->assertFalse($column->isNotNull());
     }
 
     public function testPrecision(): void
diff --git a/tests/Provider/ColumnBuilderProvider.php b/tests/Provider/ColumnBuilderProvider.php
index b147df30d..ea783d70c 100644
--- a/tests/Provider/ColumnBuilderProvider.php
+++ b/tests/Provider/ColumnBuilderProvider.php
@@ -28,7 +28,7 @@ class ColumnBuilderProvider
         'getSize' => null,
         'isAutoIncrement' => false,
         'isComputed' => false,
-        'isNotNull' => false,
+        'isNotNull' => null,
         'isPrimaryKey' => false,
         'isUnsigned' => false,
     ];
diff --git a/tests/Provider/QueryBuilderProvider.php b/tests/Provider/QueryBuilderProvider.php
index 63b22d580..c6161d200 100644
--- a/tests/Provider/QueryBuilderProvider.php
+++ b/tests/Provider/QueryBuilderProvider.php
@@ -1663,10 +1663,12 @@ public static function buildColumnDefinition(): array
             'comment(null)' => ['varchar(255)', ColumnBuilder::string()->comment(null)],
             "defaultValue('value')" => ["varchar(255) DEFAULT 'value'", ColumnBuilder::string()->defaultValue('value')],
             "defaultValue('')" => ["varchar(255) DEFAULT ''", ColumnBuilder::string()->defaultValue('')],
-            'defaultValue(null)' => ['varchar(255)', ColumnBuilder::string()->defaultValue(null)],
+            'defaultValue(null)' => ['varchar(255) DEFAULT NULL', ColumnBuilder::string()->defaultValue(null)],
             'defaultValue($expression)' => ['varchar(255) DEFAULT expression', ColumnBuilder::string()->defaultValue(new Expression('expression'))],
-            "integer()->defaultValue('')" => ['integer', ColumnBuilder::integer()->defaultValue('')],
+            'notNull()->defaultValue(null)' => ['varchar(255) NOT NULL', ColumnBuilder::string()->notNull()->defaultValue(null)],
+            "integer()->defaultValue('')" => ['integer DEFAULT NULL', ColumnBuilder::integer()->defaultValue('')],
             'notNull()' => ['varchar(255) NOT NULL', ColumnBuilder::string()->notNull()],
+            'null()' => ['varchar(255) NULL', ColumnBuilder::string()->null()],
             'integer()->primaryKey()' => ['integer PRIMARY KEY', ColumnBuilder::integer()->primaryKey()],
             'size(10)' => ['varchar(10)', ColumnBuilder::string()->size(10)],
             'unique()' => ['varchar(255) UNIQUE', ColumnBuilder::string()->unique()],