The COLUMNS
table provides
information about columns in tables.
INFORMATION_SCHEMA Name | SHOW Name | Remarks |
---|---|---|
TABLE_CATALOG | def | |
TABLE_SCHEMA | ||
TABLE_NAME | ||
COLUMN_NAME | Field | |
ORDINAL_POSITION | see notes | |
COLUMN_DEFAULT | Default | |
IS_NULLABLE | Null | |
DATA_TYPE | Type | |
CHARACTER_MAXIMUM_LENGTH | Type | |
CHARACTER_OCTET_LENGTH | ||
NUMERIC_PRECISION | Type | |
NUMERIC_SCALE | Type | |
CHARACTER_SET_NAME | ||
COLLATION_NAME | Collation | |
COLUMN_TYPE | Type | MySQL extension |
COLUMN_KEY | Key | MySQL extension |
EXTRA | Extra | MySQL extension |
PRIVILEGES | Privileges | MySQL extension |
COLUMN_COMMENT | Comment | MySQL extension |
Notes:
In
SHOW
, theType
display includes values from several differentCOLUMNS
columns.ORDINAL_POSITION
is necessary because you might want to sayORDER BY ORDINAL_POSITION
. UnlikeSHOW
,SELECT
does not have automatic ordering.CHARACTER_OCTET_LENGTH
should be the same asCHARACTER_MAXIMUM_LENGTH
, except for multi-byte character sets.CHARACTER_SET_NAME
can be derived fromCollation
. For example, if you saySHOW FULL COLUMNS FROM t
, and you see in theCollation
column a value oflatin1_swedish_ci
, the character set is what is before the first underscore:latin1
.
The following statements are nearly equivalent:
SELECT COLUMN_NAME, DATA_TYPE, IS_NULLABLE, COLUMN_DEFAULT FROM INFORMATION_SCHEMA.COLUMNS WHERE table_name = 'tbl_name
' [AND table_schema = 'db_name
'] [AND column_name LIKE 'wild
'] SHOW COLUMNS FROMtbl_name
[FROMdb_name
] [LIKE 'wild
']