Getting table metadata in MySQL - mysql

Question

I'm trying to find out how to get the following constraint information from a table in MySQL 5.0:
primary key
foreign keys and table references
unique columns
What is the syntax of the query or queries to do so? I have a feeling I'm close with this, but there is no example.

Answer 1

For MySQL:
1) get Table/Fields metadata
SELECT table_schema, table_name, column_name, ordinal_position, data_type,
numeric_precision, column_type, column_default, is_nullable, column_comment
FROM information_schema.columns
WHERE (table_schema='schema_name' and table_name = 'table_name')
order by ordinal_position;
OR
show fields from 'table_name'
2) get Foregn Keys referenced table
SELECT `REFERENCED_TABLE_NAME`
FROM `information_schema`.`KEY_COLUMN_USAGE`
WHERE
`TABLE_NAME` = 'table_name' AND
`COLUMN_NAME` = 'Column_Name'
3) get indexes (primary and foreign) for a table
show keys from `table_name`
5) get All indexes and referreced table
SELECT *
FROM `KEY_COLUMN_USAGE`
WHERE
`TABLE_NAME` = 'table_name' AND
`TABLE_SCHEMA` = 'schema_name'
OR
SELECT *
FROM `REFERENTIAL_CONSTRAINTS`
WHERE
`TABLE_NAME` = 'table_name' AND
`CONSTRAINT_SCHEMA` = 'schema_name'
6) get STORED PROCEDURES
SELECT *
FROM `ROUTINES`
WHERE
`ROUTINE_SCHEMA` = 'schema_name'
7) get TRIGGERS
SELECT *
FROM `TRIGGERS`
WHERE
`TRIGGER_SCHEMA` = 'schema_name'
8) get EVENTS
SELECT *
FROM `EVENTS`
WHERE
`EVENT_SCHEMA` = 'schema_name'
9) get VIEWS
SELECT *
FROM `VIEWS`
WHERE
`TABLE_NAME` = 'table_name' AND
`TABLE_SCHEMA` = 'schema_name'

Answer 2

The SHOW COLUMNS command will show you the primary key and unique columns for a table.
As for foreign keys, you could use something like the SHOW CREATE TABLE command which will output the DDL statements needed to replicate the table.

Answer 3

Use
show fields from table_name
show keys from table_name
to get primary keys, foreign keys, unique, etc.
to get the table referenced by a foreign key use:
SELECT `REFERENCED_TABLE_NAME`
FROM `information_schema`.`KEY_COLUMN_USAGE`
WHERE
`TABLE_NAME` = '[table_containing_foreign_key]' AND
`COLUMN_NAME` = '[foreign_key]'
substituting [table_containing_foreign_key] and [foreign_key] with your values

Answer 4

use the following to get the same using Select Query:
SELECT table_schema, table_name, column_name, ordinal_position, data_type, numeric_precision, column_type FROM information_schema.columns WHERE table_name = '[TABLE_NAME]';

Answer 5

You should try it and see. INFORMATION_SCHEMA is part of some standard and is supported in a (mostly) similar way in other databases; this standard should be documented - you can look for that doc.
But mainly the way would be to create a bunch of test tables, and then have a look at INFORMATION_SCHEMA to see what's there.