# Class yii\db\mysql\ColumnSchemaBuilder

Inheritance | yii\db\mysql\ColumnSchemaBuilder » yii\db\ColumnSchemaBuilder » yii\base\BaseObject
Implements | yii\base\Configurable
Available since version | 2.0.8
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/db/mysql/ColumnSchemaBuilder.php

ColumnSchemaBuilder is the schema builder for MySQL databases.

## Public Properties

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Property | Type | Description | Defined By
--- | --- | --- | ---
$categoryMap | array | Mapping of abstract column types (keys) to type categories (values). | yii\db\ColumnSchemaBuilder
$comment | string | Comment value of the column. | yii\db\ColumnSchemaBuilder
$db | yii\db\Connection | The current database connection. | yii\db\ColumnSchemaBuilder

## Protected Properties

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Property | Type | Description | Defined By
--- | --- | --- | ---
$after | string | The column after which this column will be added. | yii\db\ColumnSchemaBuilder
$append | mixed | SQL string to be appended to column schema definition. | yii\db\ColumnSchemaBuilder
$check | string | The `CHECK` constraint for the column. | yii\db\ColumnSchemaBuilder
$default | mixed | Default value of the column. | yii\db\ColumnSchemaBuilder
$isFirst | boolean | Whether this column is to be inserted at the beginning of the table. | yii\db\ColumnSchemaBuilder
$isNotNull | boolean|null | Whether the column is or not nullable. | yii\db\ColumnSchemaBuilder
$isUnique | boolean | Whether the column values should be unique. | yii\db\ColumnSchemaBuilder
$isUnsigned | boolean | Whether the column values should be unsigned. | yii\db\ColumnSchemaBuilder
$length | integer|string|array | Column size or precision definition. | yii\db\ColumnSchemaBuilder
$type | string | The column type definition such as INTEGER, VARCHAR, DATETIME, etc. | yii\db\ColumnSchemaBuilder

## Public Methods

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Method | Description | Defined By
--- | --- | ---
__call() | Calls the named method which is not a class method. | yii\base\BaseObject
__construct() | Constructor. | yii\base\BaseObject
__get() | Returns the value of an object property. | yii\base\BaseObject
__isset() | Checks if a property is set, i.e. defined and not null. | yii\base\BaseObject
__set() | Sets value of an object property. | yii\base\BaseObject
__toString() | Builds the full string for the column's schema. | yii\db\mysql\ColumnSchemaBuilder
__unset() | Sets an object property to null. | yii\base\BaseObject
after() | Adds an `AFTER` constraint to the column. | yii\db\ColumnSchemaBuilder
append() | Specify additional SQL to be appended to column definition. | yii\db\ColumnSchemaBuilder
canGetProperty() | Returns a value indicating whether a property can be read. | yii\base\BaseObject
canSetProperty() | Returns a value indicating whether a property can be set. | yii\base\BaseObject
check() | Sets a `CHECK` constraint for the column. | yii\db\ColumnSchemaBuilder
className() | Returns the fully qualified name of this class. | yii\base\BaseObject
comment() | Specifies the comment for column. | yii\db\ColumnSchemaBuilder
defaultExpression() | Specify the default SQL expression for the column. | yii\db\ColumnSchemaBuilder
defaultValue() | Specify the default value for the column. | yii\db\ColumnSchemaBuilder
first() | Adds an `FIRST` constraint to the column. | yii\db\ColumnSchemaBuilder
hasMethod() | Returns a value indicating whether a method is defined. | yii\base\BaseObject
hasProperty() | Returns a value indicating whether a property is defined. | yii\base\BaseObject
init() | Initializes the object. | yii\base\BaseObject
notNull() | Adds a `NOT NULL` constraint to the column. | yii\db\ColumnSchemaBuilder
null() | Adds a `NULL` constraint to the column. | yii\db\ColumnSchemaBuilder
unique() | Adds a `UNIQUE` constraint to the column. | yii\db\ColumnSchemaBuilder
unsigned() | Marks column as unsigned. | yii\db\ColumnSchemaBuilder

## Protected Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
buildAfterString() | Builds the after constraint for the column. Defaults to unsupported. | yii\db\mysql\ColumnSchemaBuilder
buildAppendString() | Builds the custom string that's appended to column definition. | yii\db\ColumnSchemaBuilder
buildCheckString() | Builds the check constraint for the column. | yii\db\ColumnSchemaBuilder
buildCommentString() | Builds the comment specification for the column. | yii\db\mysql\ColumnSchemaBuilder
buildCompleteString() | Returns the complete column definition from input format. | yii\db\ColumnSchemaBuilder
buildDefaultString() | Builds the default value specification for the column. | yii\db\ColumnSchemaBuilder
buildFirstString() | Builds the first constraint for the column. Defaults to unsupported. | yii\db\mysql\ColumnSchemaBuilder
buildLengthString() | Builds the length/precision part of the column. | yii\db\ColumnSchemaBuilder
buildNotNullString() | Builds the not null constraint for the column. | yii\db\ColumnSchemaBuilder
buildUniqueString() | Builds the unique constraint for the column. | yii\db\ColumnSchemaBuilder
buildUnsignedString() | Builds the unsigned string for column. Defaults to unsupported. | yii\db\mysql\ColumnSchemaBuilder
getTypeCategory() | Returns the category of the column type. | yii\db\ColumnSchemaBuilder

## Constants

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Constant | Value | Description | Defined By
--- | --- | --- | ---
CATEGORY_NUMERIC | 'numeric' |  | yii\db\ColumnSchemaBuilder
CATEGORY_OTHER | 'other' |  | yii\db\ColumnSchemaBuilder
CATEGORY_PK | 'pk' |  | yii\db\ColumnSchemaBuilder
CATEGORY_STRING | 'string' |  | yii\db\ColumnSchemaBuilder
CATEGORY_TIME | 'time' |  | yii\db\ColumnSchemaBuilder

## Method Details

__toString() public method

Builds the full string for the column's schema.

public string __toString ( )

buildAfterString() protected method (available since version 2.0.8)

Builds the after constraint for the column. Defaults to unsupported.

protected string buildAfterString ( )
return | string | A string containing the AFTER constraint.

buildCommentString() protected method (available since version 2.0.8)

Builds the comment specification for the column.

protected string buildCommentString ( )
return | string | A string containing the COMMENT keyword and the comment itself

buildFirstString() protected method (available since version 2.0.8)

Builds the first constraint for the column. Defaults to unsupported.

protected string buildFirstString ( )
return | string | A string containing the FIRST constraint.

buildUnsignedString() protected method (available since version 2.0.7)

Builds the unsigned string for column. Defaults to unsupported.

protected string buildUnsignedString ( )
return | string | A string containing UNSIGNED keyword.