mysql - MySQL判断主键是否存在的方法

Question

我已经尝试了几个 sql 脚本但都失败了。这是我接近的那个:

SELECT *
FROM INFORMATION_SCHEMA.STATISTICS
WHERE table_schema = schema()
AND   table_name   = 'my_table_name'
AND   index_name   = 'column_name';

Answer 1

我认为你需要以下声明

https://www.db-fiddle.com/f/jbdzXwpWkYichsBL1ib2Rj/2

select constraint_name
  from information_schema.table_constraints
 where table_name = 'mytable'
   and table_schema = 'myschema'
   and constraint_name = 'PRIMARY';

或以下 https://www.db-fiddle.com/f/jbdzXwpWkYichsBL1ib2Rj/3

SELECT EXISTS(
  SELECT 1
  FROM information_schema.columns
  WHERE 
     table_name='messages'
     and column_key = 'PRI'
) As HasPrimaryKey;