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20.3 The `INFORMATION_SCHEMA COLUMNS' Table
===========================================
The `COLUMNS' table provides information about columns in tables.
*`INFORMATION_SCHEMA' Name* *`SHOW' Name* *Remarks*
`TABLE_CATALOG' `NULL'
`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
`COLUMN_COMMENT' `Comment' MySQL extension
Notes:
* In `SHOW', the `Type' display includes values from several
different `COLUMNS' columns.
* `ORDINAL_POSITION' is necessary because you might someday want to
say `ORDER BY ORDINAL_POSITION'. Unlike `SHOW', `SELECT' does not
have automatic ordering.
* `CHARACTER_OCTET_LENGTH' should be the same as
`CHARACTER_MAXIMUM_LENGTH', except for multi-byte character sets.
* `CHARACTER_SET_NAME' can be derived from `Collation'. For example,
if you say `SHOW FULL COLUMNS FROM t', and you see in the
`Collation' column a value of `latin1_swedish_ci', the character
set is what's 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
FROM TBL_NAME
[FROM DB_NAME]
[LIKE 'WILD']
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