Question

我有一个系统可以在子查询中生成带有大量派生表的SQL查询。这是一个典型的例子：

SELECT

    COUNT(`temp_table_main`.`person_id`) AS "resp_count",
    `temp_table_main`.`SAMPLE`, 
    SUM(`temp_table_main`.`WT`) AS "resp_count_weight" ,
    SUM(`temp_table_main`.`field1`) as `field1_count`,
    (
        SELECT 
            SUM(`temp_table_field1`.`WT`) 
        FROM 
            (
                SELECT
                        `person_id`,
                    MAX(CASE when `variable` = 4 THEN `value` END) AS `field1`,
                    MAX(CASE when `variable` = 10 THEN `value` END) AS `WT`,
                    MAX(CASE when `variable` = 3 THEN `value` END) AS `SAMPLE`

                FROM
                    `4_86_data`
                GROUP BY `person_id`
            ) AS `temp_table_field1`

        WHERE `temp_table_field1`.`field1` = 1
        AND `SAMPLE` = `temp_table_main`.`SAMPLE`

    ) AS `field1_count_WT`
FROM
    (
        SELECT
                `person_id`,
            MAX(CASE when `variable` = 4 THEN `value` END) AS `field1` ,
            MAX(CASE when `variable` = 3 THEN `value` END) AS `SAMPLE` ,
            MAX(CASE when `variable` = 10 THEN `value` END) AS `WT` 
        FROM
            `4_86_data`
        GROUP by `person_id`
    ) AS `temp_table_main`
WHERE (  `field1` IS NOT NULL )  GROUP BY `SAMPLE`

我想做的是能够将其格式化为：

SELECT
    COUNT(`temp_table_main`.`person_id`) AS "resp_count",
    `temp_table_main`.`SAMPLE`, 
    SUM(`temp_table_main`.`WT`) AS "resp_count_weight" ,
    SUM(`temp_table_main`.`field1`) as `field1_count`,
    (
        SELECT 
            SUM(`temp_table_field1`.`WT`) 
        FROM 
            `temp_table_main` AS `temp_table_field1`
        WHERE `temp_table_field1`.`field1` = 1
        AND `SAMPLE` = `temp_table_main`.`SAMPLE`

    ) AS `field1_count_WT`
FROM
    (
        SELECT
                `person_id`,
            MAX(CASE when `variable` = 4 THEN `value` END) AS `field1` ,
            MAX(CASE when `variable` = 3 THEN `value` END) AS `SAMPLE` ,
            MAX(CASE when `variable` = 10 THEN `value` END) AS `WT` 
        FROM
            `4_86_data`
        GROUP by `person_id`
    ) AS `temp_table_main`
WHERE (  `field1` IS NOT NULL )  GROUP BY `SAMPLE`

您会注意到我试图在外部select语句的子查询中引用外部派生表，并将其分配给temp_table_field1。

在某些情况下，我会在外部select语句中包含N个这样的子查询，因此需要将其指定为不同的派生表名。

也许这个问题是，我可以从派生表派生一个表吗？

顺便说一下，我的sql通过拥有大量的派生表来运行并执行得很好，我只是想知道是否：

能够分配一次，多次使用
它有任何特别的区别

另请注意：我不能将这些分配为临时表。它必须在一个查询中执行。

MySQL在子查询中使用派生表而不重新定义它们

0 个答案: