### 11.1.6 Numeric Type Attributes

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 MySQL supports an extension for optionally specifying the display width of integer data types in parentheses following the base keyword for the type. For example, [`INT(4)`](integer-types.html) specifies an [`INT`](integer-types.html) with a display width of four digits. This optional display width may be used by applications to display integer values having a width less than the width specified for the column by left-padding them with spaces. (That is, this width is present in the metadata returned with result sets. Whether it is used is up to the application.)

 The display width does *not* constrain the range of values that can be stored in the column. Nor does it prevent values wider than the column display width from being displayed correctly. For example, a column specified as [`SMALLINT(3)`](integer-types.html) has the usual [`SMALLINT`](integer-types.html) range of `-32768` to `32767`, and values outside the range permitted by three digits are displayed in full using more than three digits.

 When used in conjunction with the optional (nonstandard) `ZEROFILL` attribute, the default padding of spaces is replaced with zeros. For example, for a column declared as [`INT(4) ZEROFILL`](integer-types.html), a value of `5` is retrieved as `0005`.

Note

 The `ZEROFILL` attribute is ignored for columns involved in expressions or [`UNION`](union.html) queries.

 If you store values larger than the display width in an integer column that has the `ZEROFILL` attribute, you may experience problems when MySQL generates temporary tables for some complicated joins. In these cases, MySQL assumes that the data values fit within the column display width.

 As of MySQL 8.0.17, the `ZEROFILL` attribute is deprecated for numeric data types, as is the display width attribute for integer data types. You should expect support for `ZEROFILL` and display widths for integer data types to be removed in a future version of MySQL. Consider using an alternative means of producing the effect of these attributes. For example, applications can use the [`LPAD()`](string-functions.html#function_lpad) function to zero-pad numbers up to the desired width, or they can store the formatted numbers in [`CHAR`](char.html) columns.

 All integer types can have an optional (nonstandard) `UNSIGNED` attribute. An unsigned type can be used to permit only nonnegative numbers in a column or when you need a larger upper numeric range for the column. For example, if an [`INT`](integer-types.html) column is `UNSIGNED`, the size of the column's range is the same but its endpoints shift up, from `-2147483648` and `2147483647` to `0` and `4294967295`.

 Floating-point and fixed-point types also can be `UNSIGNED`. As with integer types, this attribute prevents negative values from being stored in the column. Unlike the integer types, the upper range of column values remains the same. As of MySQL 8.0.17, the `UNSIGNED` attribute is deprecated for columns of type [`FLOAT`](floating-point-types.html), [`DOUBLE`](floating-point-types.html), and [`DECIMAL`](fixed-point-types.html) (and any synonyms) and you should expect support for it to be removed in a future version of MySQL. Consider using a simple `CHECK` constraint instead for such columns.

 If you specify `ZEROFILL` for a numeric column, MySQL automatically adds the `UNSIGNED` attribute.

 Integer or floating-point data types can have the `AUTO_INCREMENT` attribute. When you insert a value of `NULL` into an indexed `AUTO_INCREMENT` column, the column is set to the next sequence value. Typically this is `*`value`*+1`, where *`value`* is the largest value for the column currently in the table. (`AUTO_INCREMENT` sequences begin with `1`.)

 Storing `0` into an `AUTO_INCREMENT` column has the same effect as storing `NULL`, unless the [`NO_AUTO_VALUE_ON_ZERO`](sql-mode.html#sqlmode_no_auto_value_on_zero) SQL mode is enabled.

 Inserting `NULL` to generate `AUTO_INCREMENT` values requires that the column be declared `NOT NULL`. If the column is declared `NULL`, inserting `NULL` stores a `NULL`. When you insert any other value into an `AUTO_INCREMENT` column, the column is set to that value and the sequence is reset so that the next automatically generated value follows sequentially from the inserted value.

 Negative values for `AUTO_INCREMENT` columns are not supported.

`CHECK` constraints cannot refer to columns that have the `AUTO_INCREMENT` attribute, nor can the `AUTO_INCREMENT` attribute be added to existing columns that are used in `CHECK` constraints.

 As of MySQL 8.0.17, `AUTO_INCREMENT` support is deprecated for [`FLOAT`](floating-point-types.html) and [`DOUBLE`](floating-point-types.html) columns; you should expect it to be removed in a future version of MySQL. Consider removing the `AUTO_INCREMENT` attribute from such columns, or convert them to an integer type.

