columns

columns contains information about all table columns (or view columns).

:::note The metadata of synchronous materialized views is not recorded in columns. You can access it by executing SHOW PROC '/dbs/db/table/index_schema'. :::

The following fields are provided in columns:

Field	Description
TABLE_CATALOG	The name of the catalog to which the table containing the column belongs. This value is always NULL.
TABLE_SCHEMA	The name of the database to which the table containing the column belongs.
TABLE_NAME	The name of the table containing the column.
COLUMN_NAME	The name of the column.
ORDINAL_POSITION	The ordinal position of the column within the table.
COLUMN_DEFAULT	The default value for the column. This is NULL if the column has an explicit default of NULL, or if the column definition includes no DEFAULT clause.
IS_NULLABLE	The column nullability. The value is YES if NULL values can be stored in the column, NO if not.
DATA_TYPE	The column data type. The DATA_TYPE value is the type name only with no other information. The COLUMN_TYPE value contains the type name and possibly other information such as the precision or length.
CHARACTER_MAXIMUM_LENGTH	For string columns, the maximum length in characters.
CHARACTER_OCTET_LENGTH	For string columns, the maximum length in bytes.
NUMERIC_PRECISION	For numeric columns, the numeric precision.
NUMERIC_SCALE	For numeric columns, the numeric scale.
DATETIME_PRECISION	For temporal columns, the fractional seconds precision.
CHARACTER_SET_NAME	For character string columns, the character set name.
COLLATION_NAME	For character string columns, the collation name.
COLUMN_TYPE	The column data type.
The DATA_TYPE value is the type name only with no other information. The COLUMN_TYPE value contains the type name and possibly other information such as the precision or length.
COLUMN_KEY	Whether the column is indexed:<ul><li>If COLUMN_KEY is empty, the column either is not indexed or is indexed only as a secondary column in a multiple-column, nonunique index.</li><li>If COLUMN_KEY is PRI, the column is a PRIMARY KEY or is one of the columns in a multiple-column PRIMARY KEY.</li><li>If COLUMN_KEY is UNI, the column is the first column of a UNIQUE index. (A UNIQUE index permits multiple NULL values, but you can tell whether the column permits NULL by checking the Null column.)</li><li>If COLUMN_KEY is DUP, the column is the first column of a nonunique index in which multiple occurrences of a given value are permitted within the column.</li></ul>If more than one of the COLUMN_KEY values applies to a given column of a table, COLUMN_KEY displays the one with the highest priority, in the order PRI, UNI, DUP.
A UNIQUE index may be displayed as PRI if it cannot contain NULL values and there is no PRIMARY KEY in the table. A UNIQUE index may display as MUL if several columns form a composite UNIQUE index; although the combination of the columns is unique, each column can still hold multiple occurrences of a given value.
EXTRA	Any additional information that is available about a given column.
PRIVILEGES	The privileges you have for the column.
COLUMN_COMMENT	The comments of the column.
COLUMN_SIZE	The maximum length of the column in bytes.
DECIMAL_DIGITS	The number of fractional digits for numeric types.
GENERATION_EXPRESSION	The expression used to generate the column's value.
SRS_ID	The spatial reference system identifier for spatial columns.
COLUMN_SIZE
DECIMAL_DIGITS
GENERATION_EXPRESSION	For generated columns, displays the expression used to compute column values. Empty for nongenerated columns.
SRS_ID	This value applies to spatial columns. It contains the column SRID value that indicates the spatial reference system for values stored in the column.