diff --git a/CHANGELOG.md b/CHANGELOG.md
index 741141d..e057607 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,14 +11,16 @@
 - Chg #272: Replace call of `SchemaInterface::getRawTableName()` to `QuoterInterface::getRawTableName()` (@Tigrov)
 - Enh #275: Refactor PHP type of `ColumnSchemaInterface` instances (@Tigrov)
 - Enh #277: Raise minimum PHP version to `^8.1` with minor refactoring (@Tigrov)
-- New #276: Implement `ColumnFactory` class (@Tigrov)
+- New #276, #288: Implement `ColumnFactory` class (@Tigrov)
 - Enh #279: Separate column type constants (@Tigrov)
-- New #280: Realize `ColumnBuilder` class (@Tigrov)
+- New #280, #291: Realize `ColumnBuilder` class (@Tigrov)
 - Enh #281: Update according changes in `ColumnSchemaInterface` (@Tigrov)
-- New #282: Add `ColumnDefinitionBuilder` class (@Tigrov)
+- New #282, #291: Add `ColumnDefinitionBuilder` class (@Tigrov)
 - Bug #285: Fix `DMLQueryBuilder::insertBatch()` method (@Tigrov)
 - Enh #283: Refactor `Dsn` class (@Tigrov)
 - Enh #286: Use constructor to create columns and initialize properties (@Tigrov)
+- Enh #288: Refactor `Schema::findColumns()` method (@Tigrov)
+- Enh #289: Refactor `Schema::normalizeDefaultValue()` method and move it to `ColumnFactory` class (@Tigrov)
 
 ## 1.3.0 March 21, 2024
 
diff --git a/src/Column/ColumnBuilder.php b/src/Column/ColumnBuilder.php
index 41e9457..0e5f26b 100644
--- a/src/Column/ColumnBuilder.php
+++ b/src/Column/ColumnBuilder.php
@@ -9,26 +9,6 @@
 
 final class ColumnBuilder extends \Yiisoft\Db\Schema\Column\ColumnBuilder
 {
-    public static function tinyint(int|null $size = 3): ColumnSchemaInterface
-    {
-        return parent::tinyint($size);
-    }
-
-    public static function smallint(int|null $size = 5): ColumnSchemaInterface
-    {
-        return parent::smallint($size);
-    }
-
-    public static function integer(int|null $size = 10): ColumnSchemaInterface
-    {
-        return parent::integer($size);
-    }
-
-    public static function bigint(int|null $size = 20): ColumnSchemaInterface
-    {
-        return parent::bigint($size);
-    }
-
     public static function binary(int|null $size = null): ColumnSchemaInterface
     {
         return new BinaryColumnSchema(ColumnType::BINARY, size: $size);
diff --git a/src/Column/ColumnDefinitionBuilder.php b/src/Column/ColumnDefinitionBuilder.php
index baad503..10c5eb1 100644
--- a/src/Column/ColumnDefinitionBuilder.php
+++ b/src/Column/ColumnDefinitionBuilder.php
@@ -19,6 +19,10 @@ final class ColumnDefinitionBuilder extends AbstractColumnDefinitionBuilder
     protected const GENERATE_UUID_EXPRESSION = 'sys_guid()';
 
     protected const TYPES_WITH_SIZE = [
+        'char',
+        'nchar',
+        'character',
+        'varchar',
         'varchar2',
         'nvarchar2',
         'number',
@@ -27,8 +31,6 @@ final class ColumnDefinitionBuilder extends AbstractColumnDefinitionBuilder
         'interval day(0) to second',
         'raw',
         'urowid',
-        'char',
-        'nchar',
     ];
 
     protected const TYPES_WITH_SCALE = [
@@ -67,7 +69,7 @@ protected function getDbType(ColumnSchemaInterface $column): string
         $size = $column->getSize();
 
         /** @psalm-suppress DocblockTypeContradiction */
-        return match ($column->getType()) {
+        return $column->getDbType() ?? match ($column->getType()) {
             ColumnType::BOOLEAN => 'number(1)',
             ColumnType::BIT => match (true) {
                 $size === null => 'number(38)',
@@ -83,7 +85,7 @@ protected function getDbType(ColumnSchemaInterface $column): string
             ColumnType::DECIMAL => 'number(' . ($size ?? 10) . ',' . ($column->getScale() ?? 0) . ')',
             ColumnType::MONEY => 'number(' . ($size ?? 19) . ',' . ($column->getScale() ?? 4) . ')',
             ColumnType::CHAR => 'char',
-            ColumnType::STRING => 'varchar2',
+            ColumnType::STRING => 'varchar2(' . ($size ?? 255) . ')',
             ColumnType::TEXT => 'clob',
             ColumnType::BINARY => 'blob',
             ColumnType::UUID => 'raw(16)',
@@ -91,9 +93,9 @@ protected function getDbType(ColumnSchemaInterface $column): string
             ColumnType::TIMESTAMP => 'timestamp',
             ColumnType::DATE => 'date',
             ColumnType::TIME => 'interval day(0) to second',
-            ColumnType::ARRAY => 'json',
-            ColumnType::STRUCTURED => 'json',
-            ColumnType::JSON => 'json',
+            ColumnType::ARRAY => 'clob',
+            ColumnType::STRUCTURED => 'clob',
+            ColumnType::JSON => 'clob',
             default => 'varchar2',
         };
     }
diff --git a/src/Column/ColumnFactory.php b/src/Column/ColumnFactory.php
index 8916825..1411493 100644
--- a/src/Column/ColumnFactory.php
+++ b/src/Column/ColumnFactory.php
@@ -9,6 +9,7 @@
 use Yiisoft\Db\Schema\Column\ColumnSchemaInterface;
 
 use function preg_replace;
+use function rtrim;
 use function strtolower;
 
 final class ColumnFactory extends AbstractColumnFactory
@@ -19,12 +20,13 @@ final class ColumnFactory extends AbstractColumnFactory
      * @link https://docs.oracle.com/en/database/oracle/oracle-database/23/sqlrf/Data-Types.html
      *
      * @var string[]
-     *
-     * @psalm-suppress MissingClassConstType
+     * @psalm-var array<string, ColumnType::*>
      */
-    private const TYPE_MAP = [
+    protected const TYPE_MAP = [
         'char' => ColumnType::CHAR,
         'nchar' => ColumnType::CHAR,
+        'character' => ColumnType::CHAR,
+        'varchar' => ColumnType::STRING,
         'varchar2' => ColumnType::STRING,
         'nvarchar2' => ColumnType::STRING,
         'clob' => ColumnType::TEXT,
@@ -65,21 +67,20 @@ protected function getType(string $dbType, array $info = []): string
             return ColumnType::STRING;
         }
 
-        return self::TYPE_MAP[$dbType] ?? ColumnType::STRING;
+        return parent::getType($dbType, $info);
     }
 
-    public function fromType(string $type, array $info = []): ColumnSchemaInterface
+    protected function getColumnClass(string $type, array $info = []): string
     {
         if ($type === ColumnType::BINARY) {
-            unset($info['type']);
-            return new BinaryColumnSchema($type, ...$info);
+            return BinaryColumnSchema::class;
         }
 
-        return parent::fromType($type, $info);
+        return parent::getColumnClass($type, $info);
     }
 
-    protected function isDbType(string $dbType): bool
+    protected function normalizeNotNullDefaultValue(string $defaultValue, ColumnSchemaInterface $column): mixed
     {
-        return isset(self::TYPE_MAP[$dbType]);
+        return parent::normalizeNotNullDefaultValue(rtrim($defaultValue), $column);
     }
 }
diff --git a/src/Schema.php b/src/Schema.php
index 9060c54..b2364ea 100644
--- a/src/Schema.php
+++ b/src/Schema.php
@@ -7,7 +7,6 @@
 use Throwable;
 use Yiisoft\Db\Cache\SchemaCache;
 use Yiisoft\Db\Connection\ConnectionInterface;
-use Yiisoft\Db\Constant\ColumnType;
 use Yiisoft\Db\Constraint\CheckConstraint;
 use Yiisoft\Db\Constraint\Constraint;
 use Yiisoft\Db\Constraint\ForeignKeyConstraint;
@@ -16,7 +15,6 @@
 use Yiisoft\Db\Exception\Exception;
 use Yiisoft\Db\Exception\InvalidConfigException;
 use Yiisoft\Db\Exception\NotSupportedException;
-use Yiisoft\Db\Expression\Expression;
 use Yiisoft\Db\Helper\DbArrayHelper;
 use Yiisoft\Db\Oracle\Column\ColumnFactory;
 use Yiisoft\Db\Schema\Builder\ColumnInterface;
@@ -30,24 +28,23 @@
 use function implode;
 use function is_array;
 use function md5;
-use function preg_match;
 use function serialize;
-use function str_replace;
-use function trim;
 
 /**
  * Implements the Oracle Server specific schema, supporting Oracle Server 11C and above.
  *
- * @psalm-type ColumnInfoArray = array{
+ * @psalm-type ColumnArray = array{
  *   column_name: string,
  *   data_type: string,
  *   data_scale: string|null,
+ *   identity_column: string,
  *   size: string|null,
  *   nullable: string,
  *   data_default: string|null,
- *   is_pk: string|null,
- *   identity_column: string,
- *   column_comment: string|null
+ *   constraint_type: string|null,
+ *   column_comment: string|null,
+ *   schema: string,
+ *   table: string
  * }
  *
  * @psalm-type ConstraintArray = array<
@@ -334,6 +331,9 @@ protected function loadTableDefaultValues(string $tableName): array
      */
     protected function findColumns(TableSchemaInterface $table): bool
     {
+        $schemaName = $table->getSchemaName();
+        $tableName = $table->getName();
+
         $sql = <<<SQL
         SELECT
             A.COLUMN_NAME,
@@ -343,30 +343,45 @@ protected function findColumns(TableSchemaInterface $table): bool
             (CASE WHEN A.CHAR_LENGTH > 0 THEN A.CHAR_LENGTH ELSE A.DATA_PRECISION END) AS "size",
             A.NULLABLE,
             A.DATA_DEFAULT,
-            (
-                SELECT COUNT(*)
-                FROM ALL_CONSTRAINTS AC
-                INNER JOIN ALL_CONS_COLUMNS ACC ON ACC.CONSTRAINT_NAME=AC.CONSTRAINT_NAME
-                WHERE
-                     AC.OWNER = A.OWNER
-                   AND AC.TABLE_NAME = B.OBJECT_NAME
-                   AND ACC.COLUMN_NAME = A.COLUMN_NAME
-                   AND AC.CONSTRAINT_TYPE = 'P'
-            ) AS IS_PK,
+            AC.CONSTRAINT_TYPE,
             COM.COMMENTS AS COLUMN_COMMENT
         FROM ALL_TAB_COLUMNS A
-            INNER JOIN ALL_OBJECTS B ON B.OWNER = A.OWNER AND LTRIM(B.OBJECT_NAME) = LTRIM(A.TABLE_NAME)
-            LEFT JOIN ALL_COL_COMMENTS COM ON (A.OWNER = COM.OWNER AND A.TABLE_NAME = COM.TABLE_NAME AND A.COLUMN_NAME = COM.COLUMN_NAME)
-        WHERE
-            A.OWNER = :schemaName
+        INNER JOIN ALL_OBJECTS B
+            ON B.OWNER = A.OWNER
+            AND B.OBJECT_NAME = A.TABLE_NAME
+        LEFT JOIN ALL_COL_COMMENTS COM
+            ON COM.OWNER = A.OWNER
+            AND COM.TABLE_NAME = A.TABLE_NAME
+            AND COM.COLUMN_NAME = A.COLUMN_NAME
+        LEFT JOIN ALL_CONSTRAINTS AC
+            ON AC.OWNER = A.OWNER
+            AND AC.TABLE_NAME = A.TABLE_NAME
+            AND (AC.CONSTRAINT_TYPE = 'P'
+                OR AC.CONSTRAINT_TYPE = 'U'
+                AND (
+                    SELECT COUNT(*)
+                    FROM ALL_CONS_COLUMNS UCC
+                    WHERE UCC.CONSTRAINT_NAME = AC.CONSTRAINT_NAME
+                        AND UCC.TABLE_NAME = AC.TABLE_NAME
+                        AND UCC.OWNER = AC.OWNER
+                ) = 1
+            )
+            AND AC.CONSTRAINT_NAME IN (
+                SELECT ACC.CONSTRAINT_NAME
+                FROM ALL_CONS_COLUMNS ACC
+                WHERE ACC.OWNER = A.OWNER
+                    AND ACC.TABLE_NAME = A.TABLE_NAME
+                    AND ACC.COLUMN_NAME = A.COLUMN_NAME
+            )
+        WHERE A.OWNER = :schemaName
+            AND A.TABLE_NAME = :tableName
             AND B.OBJECT_TYPE IN ('TABLE', 'VIEW', 'MATERIALIZED VIEW')
-            AND B.OBJECT_NAME = :tableName
         ORDER BY A.COLUMN_ID
         SQL;
 
         $columns = $this->db->createCommand($sql, [
-            ':tableName' => $table->getName(),
-            ':schemaName' => $table->getSchemaName(),
+            ':schemaName' => $schemaName,
+            ':tableName' => $tableName,
         ])->queryAll();
 
         if ($columns === []) {
@@ -375,9 +390,12 @@ protected function findColumns(TableSchemaInterface $table): bool
 
         /** @psalm-var string[][] $info */
         foreach ($columns as $info) {
-            /** @psalm-var ColumnInfoArray $info */
             $info = array_change_key_case($info);
 
+            $info['schema'] = $schemaName;
+            $info['table'] = $tableName;
+
+            /** @psalm-var ColumnArray $info */
             $column = $this->loadColumnSchema($info);
 
             $table->column($info['column_name'], $column);
@@ -422,57 +440,23 @@ protected function getTableSequenceName(string $tableName): string|null
      *
      * @return ColumnSchemaInterface The column schema object.
      *
-     * @psalm-param ColumnInfoArray $info The column information.
+     * @psalm-param ColumnArray $info The column information.
      */
     private function loadColumnSchema(array $info): ColumnSchemaInterface
     {
-        $columnFactory = $this->db->getSchema()->getColumnFactory();
-
-        $dbType = $info['data_type'];
-        $column = $columnFactory->fromDbType($dbType, [
+        return $this->getColumnFactory()->fromDbType($info['data_type'], [
+            'autoIncrement' => $info['identity_column'] === 'YES',
+            'comment' => $info['column_comment'],
+            'defaultValueRaw' => $info['data_default'],
+            'name' => $info['column_name'],
+            'notNull' => $info['nullable'] !== 'Y',
+            'primaryKey' => $info['constraint_type'] === 'P',
             'scale' => $info['data_scale'] !== null ? (int) $info['data_scale'] : null,
+            'schema' => $info['schema'],
             'size' => $info['size'] !== null ? (int) $info['size'] : null,
+            'table' => $info['table'],
+            'unique' => $info['constraint_type'] === 'U',
         ]);
-        /** @psalm-suppress DeprecatedMethod */
-        $column->name($info['column_name']);
-        $column->notNull($info['nullable'] !== 'Y');
-        $column->comment($info['column_comment']);
-        $column->primaryKey((bool) $info['is_pk']);
-        $column->autoIncrement($info['identity_column'] === 'YES');
-        $column->defaultValue($this->normalizeDefaultValue($info['data_default'], $column));
-
-        return $column;
-    }
-
-    /**
-     * Converts column's default value according to {@see ColumnSchema::phpType} after retrieval from the database.
-     *
-     * @param string|null $defaultValue The default value retrieved from the database.
-     * @param ColumnSchemaInterface $column The column schema object.
-     *
-     * @return mixed The normalized default value.
-     */
-    private function normalizeDefaultValue(string|null $defaultValue, ColumnSchemaInterface $column): mixed
-    {
-        if ($defaultValue === null || $column->isPrimaryKey()) {
-            return null;
-        }
-
-        $defaultValue = trim($defaultValue);
-
-        if ($defaultValue === 'NULL') {
-            return null;
-        }
-
-        if ($column->getType() === ColumnType::TIMESTAMP && $defaultValue === 'CURRENT_TIMESTAMP') {
-            return new Expression($defaultValue);
-        }
-
-        if (preg_match("/^'(.*)'$/s", $defaultValue, $matches) === 1) {
-            $defaultValue = str_replace("''", "'", $matches[1]);
-        }
-
-        return $column->phpTypecast($defaultValue);
     }
 
     /**
diff --git a/tests/ColumnFactoryTest.php b/tests/ColumnFactoryTest.php
index 3cbaaf3..78d8e6b 100644
--- a/tests/ColumnFactoryTest.php
+++ b/tests/ColumnFactoryTest.php
@@ -4,6 +4,8 @@
 
 namespace Yiisoft\Db\Oracle\Tests;
 
+use PHPUnit\Framework\Attributes\DataProviderExternal;
+use Yiisoft\Db\Oracle\Tests\Provider\ColumnFactoryProvider;
 use Yiisoft\Db\Oracle\Tests\Support\TestTrait;
 use Yiisoft\Db\Tests\AbstractColumnFactoryTest;
 
@@ -14,13 +16,13 @@ final class ColumnFactoryTest extends AbstractColumnFactoryTest
 {
     use TestTrait;
 
-    /** @dataProvider \Yiisoft\Db\Oracle\Tests\Provider\ColumnFactoryProvider::dbTypes */
+    #[DataProviderExternal(ColumnFactoryProvider::class, 'dbTypes')]
     public function testFromDbType(string $dbType, string $expectedType, string $expectedInstanceOf): void
     {
         parent::testFromDbType($dbType, $expectedType, $expectedInstanceOf);
     }
 
-    /** @dataProvider \Yiisoft\Db\Oracle\Tests\Provider\ColumnFactoryProvider::definitions */
+    #[DataProviderExternal(ColumnFactoryProvider::class, 'definitions')]
     public function testFromDefinition(
         string $definition,
         string $expectedType,
@@ -30,7 +32,7 @@ public function testFromDefinition(
         parent::testFromDefinition($definition, $expectedType, $expectedInstanceOf, $expectedMethodResults);
     }
 
-    /** @dataProvider \Yiisoft\Db\Oracle\Tests\Provider\ColumnFactoryProvider::pseudoTypes */
+    #[DataProviderExternal(ColumnFactoryProvider::class, 'pseudoTypes')]
     public function testFromPseudoType(
         string $pseudoType,
         string $expectedType,
@@ -40,9 +42,15 @@ public function testFromPseudoType(
         parent::testFromPseudoType($pseudoType, $expectedType, $expectedInstanceOf, $expectedMethodResults);
     }
 
-    /** @dataProvider \Yiisoft\Db\Oracle\Tests\Provider\ColumnFactoryProvider::types */
+    #[DataProviderExternal(ColumnFactoryProvider::class, 'types')]
     public function testFromType(string $type, string $expectedType, string $expectedInstanceOf): void
     {
         parent::testFromType($type, $expectedType, $expectedInstanceOf);
     }
+
+    #[DataProviderExternal(ColumnFactoryProvider::class, 'defaultValueRaw')]
+    public function testFromTypeDefaultValueRaw(string $type, string|null $defaultValueRaw, mixed $expected): void
+    {
+        parent::testFromTypeDefaultValueRaw($type, $defaultValueRaw, $expected);
+    }
 }
diff --git a/tests/ColumnSchemaTest.php b/tests/ColumnSchemaTest.php
index 6977bd6..ebfb9ca 100644
--- a/tests/ColumnSchemaTest.php
+++ b/tests/ColumnSchemaTest.php
@@ -69,7 +69,7 @@ public function testPhpTypeCast(): void
         $db->close();
     }
 
-    public function testColumnSchemaInstance()
+    public function testColumnSchemaInstance(): void
     {
         $db = $this->getConnection(true);
         $schema = $db->getSchema();
@@ -82,18 +82,18 @@ public function testColumnSchemaInstance()
     }
 
     /** @dataProvider \Yiisoft\Db\Oracle\Tests\Provider\ColumnSchemaProvider::predefinedTypes */
-    public function testPredefinedType(string $className, string $type, string $phpType)
+    public function testPredefinedType(string $className, string $type, string $phpType): void
     {
         parent::testPredefinedType($className, $type, $phpType);
     }
 
     /** @dataProvider \Yiisoft\Db\Oracle\Tests\Provider\ColumnSchemaProvider::dbTypecastColumns */
-    public function testDbTypecastColumns(string $className, array $values)
+    public function testDbTypecastColumns(string $className, array $values): void
     {
         parent::testDbTypecastColumns($className, $values);
     }
 
-    public function testBinaryColumnSchema()
+    public function testBinaryColumnSchema(): void
     {
         $binaryCol = new BinaryColumnSchema();
         $binaryCol->dbType('BLOB');
@@ -104,4 +104,16 @@ public function testBinaryColumnSchema()
             $binaryCol->dbTypecast(new Param("\x10\x11\x12", PDO::PARAM_LOB)),
         );
     }
+
+    public function testUniqueColumn(): void
+    {
+        $db = $this->getConnection(true);
+        $schema = $db->getSchema();
+
+        $this->assertTrue($schema->getTableSchema('T_constraints_1')?->getColumn('C_unique')->isUnique());
+        $this->assertFalse($schema->getTableSchema('T_constraints_2')?->getColumn('C_index_2_1')->isUnique());
+        $this->assertFalse($schema->getTableSchema('T_constraints_2')?->getColumn('C_index_2_2')->isUnique());
+        $this->assertTrue($schema->getTableSchema('T_upsert')?->getColumn('email')->isUnique());
+        $this->assertFalse($schema->getTableSchema('T_upsert')?->getColumn('recovery_email')->isUnique());
+    }
 }
diff --git a/tests/Provider/ColumnBuilderProvider.php b/tests/Provider/ColumnBuilderProvider.php
index 41bbb5e..a846cde 100644
--- a/tests/Provider/ColumnBuilderProvider.php
+++ b/tests/Provider/ColumnBuilderProvider.php
@@ -12,16 +12,6 @@ public static function buildingMethods(): array
     {
         $values = parent::buildingMethods();
 
-        $values['primaryKey()'][4]['getSize'] = 10;
-        $values['primaryKey(false)'][4]['getSize'] = 10;
-        $values['smallPrimaryKey()'][4]['getSize'] = 5;
-        $values['smallPrimaryKey(false)'][4]['getSize'] = 5;
-        $values['bigPrimaryKey()'][4]['getSize'] = 20;
-        $values['bigPrimaryKey(false)'][4]['getSize'] = 20;
-        $values['tinyint()'][4]['getSize'] = 3;
-        $values['smallint()'][4]['getSize'] = 5;
-        $values['integer()'][4]['getSize'] = 10;
-        $values['bigint()'][4]['getSize'] = 20;
         $values['binary()'][2] = BinaryColumnSchema::class;
         $values['binary(8)'][2] = BinaryColumnSchema::class;
 
diff --git a/tests/Provider/ColumnFactoryProvider.php b/tests/Provider/ColumnFactoryProvider.php
index 88731d4..f087085 100644
--- a/tests/Provider/ColumnFactoryProvider.php
+++ b/tests/Provider/ColumnFactoryProvider.php
@@ -5,6 +5,7 @@
 namespace Yiisoft\Db\Oracle\Tests\Provider;
 
 use Yiisoft\Db\Constant\ColumnType;
+use Yiisoft\Db\Expression\Expression;
 use Yiisoft\Db\Oracle\Column\BinaryColumnSchema;
 use Yiisoft\Db\Schema\Column\DoubleColumnSchema;
 use Yiisoft\Db\Schema\Column\StringColumnSchema;
@@ -53,4 +54,16 @@ public static function definitions(): array
 
         return $definitions;
     }
+
+    public static function defaultValueRaw(): array
+    {
+        $defaultValueRaw = parent::defaultValueRaw();
+
+        $defaultValueRaw[] = [ColumnType::STRING, 'NULL ', null];
+        $defaultValueRaw[] = [ColumnType::STRING, "'str''ing' ", "str'ing"];
+        $defaultValueRaw[] = [ColumnType::INTEGER, '-1 ', -1];
+        $defaultValueRaw[] = [ColumnType::TIMESTAMP, 'now() ', new Expression('now()')];
+
+        return $defaultValueRaw;
+    }
 }
diff --git a/tests/Provider/QueryBuilderProvider.php b/tests/Provider/QueryBuilderProvider.php
index 2201d39..95da6dc 100644
--- a/tests/Provider/QueryBuilderProvider.php
+++ b/tests/Provider/QueryBuilderProvider.php
@@ -248,7 +248,7 @@ public static function buildColumnDefinition(): array
         $values[PseudoType::UBIGPK][0] = 'number(20) GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY';
         $values[PseudoType::UUID_PK][0] = 'raw(16) DEFAULT sys_guid() PRIMARY KEY';
         $values[PseudoType::UUID_PK_SEQ][0] = 'raw(16) DEFAULT sys_guid() PRIMARY KEY';
-        $values['STRING'][0] = 'varchar2';
+        $values['STRING'][0] = 'varchar2(255)';
         $values['STRING(100)'][0] = 'varchar2(100)';
         $values['primaryKey()'][0] = 'number(10) GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY';
         $values['primaryKey(false)'][0] = 'number(10) PRIMARY KEY';
@@ -263,7 +263,7 @@ public static function buildColumnDefinition(): array
         $values['bit()'][0] = 'number(38)';
         $values['bit(1)'][0] = 'number(1)';
         $values['bit(8)'][0] = 'number(3)';
-        $values['bit(1000)'][0] = 'raw(125)';
+        $values['bit(64)'][0] = 'number(20)';
         $values['tinyint()'][0] = 'number(3)';
         $values['tinyint(2)'][0] = 'number(2)';
         $values['smallint()'][0] = 'number(5)';
@@ -288,7 +288,7 @@ public static function buildColumnDefinition(): array
         $values['money(null)'][0] = 'number(19,4)';
         $values['string()'][0] = 'varchar2(255)';
         $values['string(100)'][0] = 'varchar2(100)';
-        $values['string(null)'][0] = 'varchar2';
+        $values['string(null)'][0] = 'varchar2(255)';
         $values['text()'][0] = 'clob';
         $values['text(1000)'][0] = 'clob';
         $values['binary()'][0] = 'blob';
@@ -300,21 +300,28 @@ public static function buildColumnDefinition(): array
         $values['time()'][0] = 'interval day(0) to second(0)';
         $values['time(6)'][0] = 'interval day(0) to second(6)';
         $values['time(null)'][0] = 'interval day(0) to second';
+        $values['array()'][0] = 'clob';
+        $values['structured()'][0] = 'clob';
+        $values["structured('json')"] = ['blob', ColumnBuilder::structured('blob')];
+        $values['json()'][0] = 'clob';
+        $values['json(100)'][0] = 'clob';
+        $values["extra('NOT NULL')"][0] = 'varchar2(255) NOT NULL';
+        $values["extra('')"][0] = 'varchar2(255)';
+        $values["check('value > 5')"][0] = 'number(10) CHECK ("col_59" > 5)';
+        $values["check('')"][0] = 'number(10)';
+        $values['check(null)'][0] = 'number(10)';
         $values["comment('comment')"][0] = 'varchar2(255)';
         $values["comment('')"][0] = 'varchar2(255)';
         $values['comment(null)'][0] = 'varchar2(255)';
-        $values["extra('bar')"][0] = 'varchar2(255) bar';
-        $values["extra('')"][0] = 'varchar2(255)';
-        $values["check('value > 5')"][0] = 'varchar2(255) CHECK (value > 5)';
-        $values["check('')"][0] = 'varchar2(255)';
-        $values['check(null)'][0] = 'varchar2(255)';
         $values["defaultValue('value')"][0] = "varchar2(255) DEFAULT 'value'";
         $values["defaultValue('')"][0] = "varchar2(255) DEFAULT ''";
-        $values['defaultValue(null)'][0] = 'varchar2(255)';
-        $values['defaultValue($expression)'][0] = 'varchar2(255) DEFAULT expression';
+        $values['defaultValue(null)'][0] = 'varchar2(255) DEFAULT NULL';
+        $values['defaultValue($expression)'][0] = 'number(10) DEFAULT (1 + 2)';
+        $values['notNull()->defaultValue(null)'][0] = 'varchar2(255) NOT NULL';
         $values['notNull()'][0] = 'varchar2(255) NOT NULL';
+        $values['null()'][0] = 'varchar2(255) NULL';
         $values['integer()->primaryKey()'][0] = 'number(10) PRIMARY KEY';
-        $values["integer()->defaultValue('')"][0] = 'number(10)';
+        $values["integer()->defaultValue('')"][0] = 'number(10) DEFAULT NULL';
         $values['size(10)'][0] = 'varchar2(10)';
         $values['unique()'][0] = 'varchar2(255) UNIQUE';
         $values['unsigned()'][0] = 'number(10)';
diff --git a/tests/Provider/SchemaProvider.php b/tests/Provider/SchemaProvider.php
index ab426a0..8a406d8 100644
--- a/tests/Provider/SchemaProvider.php
+++ b/tests/Provider/SchemaProvider.php
@@ -169,7 +169,7 @@ public static function columns(): array
                         'enumValues' => null,
                         'size' => null,
                         'scale' => 6,
-                        'defaultValue' => "to_timestamp('2002-01-01 00:00:00', 'yyyy-mm-dd hh24:mi:ss')",
+                        'defaultValue' => new Expression("to_timestamp('2002-01-01 00:00:00', 'yyyy-mm-dd hh24:mi:ss')"),
                     ],
                     'time_col' => [
                         'type' => 'time',
@@ -181,7 +181,7 @@ public static function columns(): array
                         'enumValues' => null,
                         'size' => 0,
                         'scale' => 0,
-                        'defaultValue' => "INTERVAL '0 10:33:21' DAY(0) TO SECOND(0)",
+                        'defaultValue' => new Expression("INTERVAL '0 10:33:21' DAY(0) TO SECOND(0)"),
                     ],
                     'interval_day_col' => [
                         'type' => 'string',
@@ -193,7 +193,7 @@ public static function columns(): array
                         'enumValues' => null,
                         'size' => 1,
                         'scale' => 0,
-                        'defaultValue' => "INTERVAL '2 04:56:12' DAY(1) TO SECOND(0)",
+                        'defaultValue' => new Expression("INTERVAL '2 04:56:12' DAY(1) TO SECOND(0)"),
                     ],
                     'bool_col' => [
                         'type' => 'char',
@@ -278,15 +278,6 @@ public static function columns(): array
         ];
     }
 
-    public static function columnsTypeChar(): array
-    {
-        return [
-            ['char_col', 'char', 100, 'CHAR'],
-            ['char_col2', 'string', 100, 'VARCHAR2'],
-            ['char_col3', 'string', 4000, 'VARCHAR2'],
-        ];
-    }
-
     public static function constraints(): array
     {
         $constraints = parent::constraints();
diff --git a/tests/SchemaTest.php b/tests/SchemaTest.php
index 40e909d..a95e978 100644
--- a/tests/SchemaTest.php
+++ b/tests/SchemaTest.php
@@ -81,18 +81,6 @@ public function testGetSchemaDefaultValues(): void
         parent::testGetSchemaDefaultValues();
     }
 
-    /**
-     * @dataProvider \Yiisoft\Db\Oracle\Tests\Provider\SchemaProvider::columnsTypeChar
-     */
-    public function testGetStringFieldsSize(
-        string $columnName,
-        string $columnType,
-        int|null $columnSize,
-        string $columnDbType
-    ): void {
-        parent::testGetStringFieldsSize($columnName, $columnType, $columnSize, $columnDbType);
-    }
-
     /**
      * @throws Exception
      * @throws InvalidConfigException