如何使用"SHOW COLUMNS"作为表的有效数据源?
mysqlmysqli database
为此，您可以使用 INFORMATION_SCHEMA.COLUMNS，如以下语法所示 −
SELECT *FROM (SELECT *FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME= 'yourTableName') anyAliasName;
首先我们创建一个表:
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)
以下是使用"SHOW COLUMNS"作为有效数据源的查询 −
mysql> SELECT *FROM (SELECT *FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME= 'DemoTable')tbl;
这将产生以下输出 −
+---------------+--------------+-------------+------------------+------------------+----------------+-------------+-----------+--------------------------+------------------------+-------------------+---------------+--------------------+--------------------+-----------------+-------------+------------+----------------+---------------------------------+----------------+-----------------------+--------+ | 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)
