I want to get the result of Desc for only specific columns of each table in the information schema, let's say Primary Key.
Can this be done?
I tried things like
SELECT * FROM (DESC TABLENAME) WHERE ....;
but it did not work.
Also I want this to work for all tables.
DESC aka DESCRIBE aka SHOW COLUMNS will not work in a subquery.
But SELECT will.
You can for example replace
SHOW COLUMNS FROM t IN test LIKE '%2';
with
SELECT column_name AS `Field`, column_type AS `Type`,
is_nullable AS `Null`,
column_key as 'Key',
column_default AS `Default`, extra AS `Extra`
FROM information_schema.columns
WHERE table_schema = 'test'
AND table_name = 't'
AND column_name like '%2';
and you'll get the same thing.
Related
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.
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'
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.
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
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]';
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.
I am looking for a query which gives me the primary key of all tables from a database, at the same order that it was created, for example:
CREATE TABLE a_antennaport
...
PRIMARY KEY (dateday,neid,cn,srn,sn,pn)
I need as output the fields in the same order:
dateday,neid,cn,srn,sn,pn
I already tried:
SELECT GROUP_CONCAT(COLUMN_NAME), TABLE_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE
TABLE_SCHEMA = schema()
AND CONSTRAINT_NAME='PRIMARY'
GROUP BY TABLE_NAME;
Your query should work already (in fact, it does. Tested, to be sure). Only thing you can improve to make sure, that the columns are in the right order, is to order by the ordinal position in the group_concat().
SELECT GROUP_CONCAT(COLUMN_NAME ORDER BY ORDINAL_POSITION), TABLE_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE
TABLE_SCHEMA = schema()
AND CONSTRAINT_NAME='PRIMARY'
GROUP BY TABLE_NAME;
I am getting all the columns of all tables listed down of my data base with following query in mySQL
SELECT * FROM information_schema.columns
WHERE table_schema = DATABASE()
ORDER BY table_name, ordinal_position
I want to get all columns whether it's a primary key or not? For primary key columns to appear as y and non primary key columns to appear as n in this query. How can I achieve that with this query?
You can use COLUMN_KEY column and CASE WHEN:
SELECT column_name, CASE WHEN COLUMN_KEY = 'PRI' THEN 'y' ELSE 'n' END AS result
FROM information_schema.columns
WHERE table_schema = DATABASE()
AND `table_name` = 'tab' -- table name
ORDER BY `table_name`, ordinal_position
SqlFiddleDemo
How to find all primary keys in all tables in a database, which don't have an auto-increment identifier to it. We have a large amount of tables and would like to identify all tables which don't have the auto increment identifier on the primary key.
You can extract this information from the information_schema.columns table
select distinct table_name
from information_schema.columns
where table_schema = 'DATABASENAME'
and table_name not in (select table_name
from information_schema.columns
where table_schema = 'DATABASENAME'
and column_key = 'PRI'
and data_type = 'int'
and extra = 'auto_increment')
This looks for all tables in one database having an auto_increment column and then returns the remaining tables. This also correctly detects tables with composite keys.
You can find that kind of information in the table information_schema.columns. The column column_key will be PRI and the column extra will contain auto_increment if it is auto incremented.
SELECT
table_schema,
table_name,
column_name
FROM
information_schema.columns
WHERE
column_key = 'PRI'
AND extra <> 'auto_increment'
AND data_type = 'int'
In this SQL Fiddle you can see that the sample table has "PRI" and "auto_increment" in the respective columns.
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.
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'
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.
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
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]';
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.