Primary Key for Mysql operations

Mysql operation primary key 1. query the primary key [html] SELECT t. TABLE_NAME, t. CONSTRAINT_TYPE, c. COLUMN_NAME, c. ORDINAL_POSITION FROM www.2cto.com INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS t, INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS c WHERE t. TABLE_NAME = c. TABLE_NAME AND t. TABLE_SCHEMA = 'database name' AND t. CONSTRAINT_TYPE = 'Primary key' and t. TABLE_NAME = 'table name'; 2. delete the primary key [html] alter table Name drop primary key; www.2cto.com 3. add a primary key [html] alter ta Ble table name add primary key (column 1, column 2...); 4. Modify the primary key first, delete the primary key, and then add your new primary key, as described in the preceding steps 2 and 3. Author fellting