如何为mysql制作DROP INDEX IF EXISTS？

Question

我想使用选项IF EXISTS在MySQL中删除INDEX，但是我没有发现任何使它成功的东西。

DROP INDEX IF EXISTS index_name ON table_name; 

任何人有任何提示吗？

Answer 1

我没有看到任何直接转到DROP INDEX使用IF EXISTS。 作为一种解决方法，我编写了以下过程，它适用于我。

CREATE PROCEDURE `DropIndexIfExists`(
    IN i_table_name VARCHAR(128), 
    IN i_index_name VARCHAR(128) 
    ) 
    BEGIN 

    SET @tableName = i_table_name; 
    SET @indexName = i_index_name; 
    SET @indexExists = 0; 

    SELECT 
     1 
    INTO @indexExists FROM 
     INFORMATION_SCHEMA.STATISTICS 
    WHERE 
     TABLE_NAME = @tableName 
      AND INDEX_NAME = @indexName; 

    SET @query = CONCAT 
    (
    ' 
    DROP INDEX ',@indexName,' ON ', @tableName,' 
    ' 
    ); 
    IF @indexExists THEN 
     PREPARE stmt FROM @query; 
     EXECUTE stmt; 
     DEALLOCATE PREPARE stmt; 
    END IF; 
    END 

Answer 2

试试这个，

create procedure DeleteIndex() 
begin 

IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.STATISTICS WHERE TABLE_NAME = 'TableName' 
      AND INDEX_NAME = 'IndexName' AND INDEX_SCHEMA='DbName') THEN 
    ALTER TABLE TableName DROP index THead2; 
END IF; 
END