How do I use `SHOW COLUMNS` as a valid data source for a table?
For this, you can use INFORMATION_SCHEMA.COLUMNS as shown in the following syntax −
SELECT *FROM (SELECT *FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME= 'yourTableName')
anyAliasName;
Let us first create a table:
mysql> create table DemoTable
(
StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY,
StudentFirstName varchar(20),
StudentLastName varchar(20),
StudentAge int
);
Query OK, 0 rows affected (1.51 sec)
Here is the query to use `SHOW COLUMNS` as a valid data source −
mysql> SELECT *FROM (SELECT *FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME= 'DemoTable')tbl;
This will produce the following output −
+---------------+--------------+-------------+------------------+------------------+----------------+-------------+-----------+--------------------------+------------------------+-------------------+---------------+--------------------+--------------------+-----------------+-------------+------------+----------------+---------------------------------+----------------+-----------------------+--------+
| TABLE_CATALOG | TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | ORDINAL_POSITION | COLUMN_DEFAULT | IS_NULLABLE | DATA_TYPE | CHARACTER_MAXIMUM_LENGTH | CHARACTER_OCTET_LENGTH | NUMERIC_PRECISION | NUMERIC_SCALE | DATETIME_PRECISION | CHARACTER_SET_NAME | COLLATION_NAME | COLUMN_TYPE | COLUMN_KEY | EXTRA | PRIVILEGES | COLUMN_COMMENT | GENERATION_EXPRESSION | SRS_ID |
+---------------+--------------+-------------+------------------+------------------+----------------+-------------+-----------+--------------------------+------------------------+-------------------+---------------+--------------------+--------------------+-----------------+-------------+------------+----------------+---------------------------------+----------------+-----------------------+--------+
| def | sample | DemoTable | StudentId | 1 | NULL | NO | int | NULL | NULL | 10 | 0 | NULL | NULL | NULL | int(11) | PRI | auto_increment | select,insert,update,references | | | NULL |
| def | sample | DemoTable | StudentFirstName | 2 | NULL | YES | varchar | 20 | 60 | NULL | NULL | NULL | utf8 | utf8_general_ci | varchar(20) | | | select,insert,update,references | | | NULL |
| def | sample | DemoTable | StudentLastName | 3 | NULL | YES | varchar | 20 | 60 | NULL | NULL | NULL | utf8 | utf8_general_ci | varchar(20) | | | select,insert,update,references | | | NULL |
| def | sample | DemoTable | StudentAge | 4 | NULL | YES | int | NULL | NULL | 10 | 0 | NULL | NULL | NULL | int(11) | | | select,insert,update,references | | | NULL |
+---------------+--------------+-------------+------------------+------------------+----------------+-------------+-----------+--------------------------+------------------------+-------------------+---------------+--------------------+--------------------+-----------------+-------------+------------+----------------+---------------------------------+----------------+-----------------------+--------+
4 rows in set (0.00 sec)
Published on 29-Apr-2019 12:47:00
