如何从存储过程创建索引或在MySQL中的每个表上创建索引？ [英] How do I create an index from a stored procedure or create index on every table in MySQL?

问题描述

这是我到目前为止尝试过的两件事，以及他们的错误消息：

These are two things that I've tried so far, along with their error messages:

DELIMITER //

CREATE PROCEDURE createModifiedIndex(t varchar(256))
  BEGIN
    declare idx varchar(256);
    DECLARE i int;
    declare makeIndexSql varchar(256);
    set idx = concat('idx_', t, '_modified_on');
    set i = (select count(*) from INFORMATION_SCHEMA.STATISTICS where table_name = t and index_name = idx);
    if i > 0 then
        set makeIndexSql = concat('create index ', idx, ' on ', t, ' (modified_on);');
        prepare stmt from makeIndexSql;
        execute stmt;
    end if;
  END //

DELIMITER ;

call createModifiedIndex ('ACHDebitFrequencies');
call createModifiedIndex ...

ERROR 1064（42000）第5行：您的SQL语法有错误;检查与您的MySQL服务器版本对应的手册，以便在'makeIndexSql附近使用正确的语法;
执行stmt;
结束如果;
END'在第10行

ERROR 1064 (42000) at line 5: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'makeIndexSql; execute stmt; end if; END' at line 10

这是另一种不同的尝试但不起作用，因为MySQL不允许IF /那么在存储过程之外。

This is another different attempt but won't work because MySQL doesn't allow IF/THEN outside of stored procedures.

set @i = (select count(*) from INFORMATION_SCHEMA.STATISTICS where table_name = 'ACHDebitFrequencies' and index_name = 'idx_ACHDebitFrequencies_modified_on');
if @i > 0 then begin
        create index 'idx_ACHDebitFrequencies_modified_on' on ACHDebitFrequencies (modified_on);
end;
end if;
...

ERROR 1064（42000）at line 3：您的SQL语法有错误;查看与您的MySQL服务器版本对应的手册，以便在'if @i> 0附近使用正确的语法然后在第1行开始
在ACHD'上创建索引'idx_ACHDebitFrequencies_modified_on'

ERROR 1064 (42000) at line 3: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'if @i > 0 then begin create index 'idx_ACHDebitFrequencies_modified_on' on ACHD' at line 1

版本mysql-5.1.62-r1

Version mysql-5.1.62-r1

推荐答案

核心问题您的过程是 PREPARE 语句仅适用于用户变量或字符串文字。它无法从过程变量中准备语句。

The core problem with your procedure was that PREPARE statement only works with a user variable or a string literal. It can't prepare a statement from a procedure variable.

PREPARE语法

PREPARE stmt_name FROM preparable_stmt

... preparable_stmt是字符串文字或用户变量，
包含SQL语句的文本。

PREPARE Syntax
PREPARE stmt_name FROM preparable_stmt
... preparable_stmt is either a string literal or a user variable that contains the text of the SQL statement.

DELIMITER //
CREATE PROCEDURE createModifiedIndex(t VARCHAR(256))
  BEGIN
    DECLARE idx VARCHAR(256);
    DECLARE i INT;

    SET idx = CONCAT('idx_', t, '_modified_on');
    SET i = (SELECT COUNT(*) FROM INFORMATION_SCHEMA.STATISTICS WHERE table_name = t AND index_name = idx);
    IF i = 0 THEN
        SET @makeIndexSql = CONCAT('CREATE INDEX ', idx, ' ON ', t, ' (modified_on);');
        PREPARE stmt FROM @makeIndexSql;
        EXECUTE stmt;
        DEALLOCATE PREPARE stmt; -- Use DEALLOCATE when you're done with the statement
    END IF;
  END //

DELIMITER ;

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