Mysql 组合三个SQL查询_Mysql_Sql

Mysql 组合三个SQL查询

mysql sql

Mysql 组合三个SQL查询,mysql,sql,Mysql,Sql,我有以下三个SQL查询。我想将它们合并为一个是可能的，或者使用当前的方法，或者如果它更有效的话，使用另一种方法注意：我需要知道所有三个WHERE子句的不同计数值查询1: SElECT COUNT(*) AS imgCount FROM ( SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images UNION ALL SELECT imgHeight, imgWidth, primaryId

我有以下三个SQL查询。我想将它们合并为一个是可能的，或者使用当前的方法，或者如果它更有效的话，使用另一种方法

注意：我需要知道所有三个WHERE子句的不同计数值

查询1:

SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth = $maxImageWidth AND imgHeight = $maxImageHeight;

SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth = $maxImageWidth AND imgHeight != $maxImageHeight;

SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth != $maxImageWidth AND imgHeight = $maxImageHeight;

查询2:

SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth = $maxImageWidth AND imgHeight = $maxImageHeight;

SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth = $maxImageWidth AND imgHeight != $maxImageHeight;

SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth != $maxImageWidth AND imgHeight = $maxImageHeight;

查询3:

SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth = $maxImageWidth AND imgHeight = $maxImageHeight;

SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth = $maxImageWidth AND imgHeight != $maxImageHeight;

SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth != $maxImageWidth AND imgHeight = $maxImageHeight;

另外，我的数据库是MySQL。我听说过使用

=并不是在所有情况下都有效，但是
更好。在我的情况下，应该=还好吗？
这可能适合您
SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId 
AND (imgWidth != $maxImageWidth AND imgHeight = $maxImageHeight
OR imgWidth = $maxImageWidth AND imgHeight != $maxImageHeight
OR imgWidth = $maxImageWidth AND imgHeight = $maxImageHeight);

我也相信这是等效的，尽管我不确定
SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId 
AND (imgWidth = $maxImageWidth OR imgHeight = $maxImageHeight);

根据请求，这里有一个返回3行的查询
SELECT 'ALL EQUAL' AS COL1,COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth = $maxImageWidth AND imgHeight = $maxImageHeight
UNION ALL
SELECT 'WIDTH EQUAL' AS COL1,COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth = $maxImageWidth AND imgHeight != $maxImageHeight;
UNION ALL
SELECT 'HEIGHT EQUAL' AS COL1,COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images  
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth != $maxImageWidth AND imgHeight = $maxImageHeight;

这可能对你有用
SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId 
AND (imgWidth != $maxImageWidth AND imgHeight = $maxImageHeight
OR imgWidth = $maxImageWidth AND imgHeight != $maxImageHeight
OR imgWidth = $maxImageWidth AND imgHeight = $maxImageHeight);

我也相信这是等效的，尽管我不确定
SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId 
AND (imgWidth = $maxImageWidth OR imgHeight = $maxImageHeight);

根据请求，这里有一个返回3行的查询
SELECT 'ALL EQUAL' AS COL1,COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth = $maxImageWidth AND imgHeight = $maxImageHeight
UNION ALL
SELECT 'WIDTH EQUAL' AS COL1,COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth = $maxImageWidth AND imgHeight != $maxImageHeight;
UNION ALL
SELECT 'HEIGHT EQUAL' AS COL1,COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images  
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images
) AS union_table
WHERE primaryId = $imgId AND imgWidth != $maxImageWidth AND imgHeight = $maxImageHeight;

我认为需要一个案例和一个小组：
SELECT CASE
       WHEN imgWidth  = $maxImageWidth AND imgHeight  = $maxImageHeight
       THEN 0
       WHEN imgWidth != $maxImageWidth AND imgHeight  = $maxImageHeight
       THEN 1
       WHEN imgWidth  = $maxImageWidth AND imgHeight != $maxImageHeight
       THEN 2
       END AS count_type,
       COUNT(*) AS imgCount
  FROM (SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
        UNION ALL 
        SELECT imgHeight, imgWidth, primaryId FROM secondary_images
       ) AS union_table
 WHERE primaryId = $imgId
   AND (imgWidth = $maxImageWidth OR imgHeight = $maxImageHeight)
 GROUP BY count_type;

将WHERE子句下推到UNION子查询中至少是很有诱惑力的，但是优化器无论如何都应该这样做。通过研究解释输出来检查它是否做到了这一点。如果优化器没有自动执行谓词下推，您将编写：
SELECT CASE
       WHEN imgWidth  = $maxImageWidth AND imgHeight  = $maxImageHeight
       THEN 0
       WHEN imgWidth != $maxImageWidth AND imgHeight  = $maxImageHeight
       THEN 1
       WHEN imgWidth  = $maxImageWidth AND imgHeight != $maxImageHeight
       THEN 2
       END AS count_type,
       COUNT(*) AS imgCount
  FROM (SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
         WHERE primaryId = $imgId  -- or: imgId = $imgId
           AND (imgWidth = $maxImageWidth OR imgHeight = $maxImageHeight)
        UNION ALL 
        SELECT imgHeight, imgWidth, primaryId FROM secondary_images
         WHERE primaryId = $imgId
           AND (imgWidth = $maxImageWidth OR imgHeight = $maxImageHeight)
       ) AS union_table
 GROUP BY count_type;

此解决方案的缺点是，$maxImageWidth
和$maxImageHeight
变量分别使用了4次（和$imgId
一次）。如果您正在准备如图所示的语句（将值嵌入表示SQL的字符串中），那么还不错。如果您正在使用占位符，则可能需要占位符的命名方案（：img\u ht
，：img\u wd
，：img\u id
（或至少：1
，：2
，：3
）来代替？
占位符），以便在EXECUTE语句中只传递每个值一次。不过，这种能力取决于您的DBMS；MySQL是许多不支持此功能的DBMS之一。
我认为需要一个案例和一个分组：
SELECT CASE
       WHEN imgWidth  = $maxImageWidth AND imgHeight  = $maxImageHeight
       THEN 0
       WHEN imgWidth != $maxImageWidth AND imgHeight  = $maxImageHeight
       THEN 1
       WHEN imgWidth  = $maxImageWidth AND imgHeight != $maxImageHeight
       THEN 2
       END AS count_type,
       COUNT(*) AS imgCount
  FROM (SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
        UNION ALL 
        SELECT imgHeight, imgWidth, primaryId FROM secondary_images
       ) AS union_table
 WHERE primaryId = $imgId
   AND (imgWidth = $maxImageWidth OR imgHeight = $maxImageHeight)
 GROUP BY count_type;

将WHERE子句下推到UNION子查询中至少是很有诱惑力的，但是优化器无论如何都应该这样做。通过研究解释输出来检查它是否做到了这一点。如果优化器没有自动执行谓词下推，您将编写：
SELECT CASE
       WHEN imgWidth  = $maxImageWidth AND imgHeight  = $maxImageHeight
       THEN 0
       WHEN imgWidth != $maxImageWidth AND imgHeight  = $maxImageHeight
       THEN 1
       WHEN imgWidth  = $maxImageWidth AND imgHeight != $maxImageHeight
       THEN 2
       END AS count_type,
       COUNT(*) AS imgCount
  FROM (SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images
         WHERE primaryId = $imgId  -- or: imgId = $imgId
           AND (imgWidth = $maxImageWidth OR imgHeight = $maxImageHeight)
        UNION ALL 
        SELECT imgHeight, imgWidth, primaryId FROM secondary_images
         WHERE primaryId = $imgId
           AND (imgWidth = $maxImageWidth OR imgHeight = $maxImageHeight)
       ) AS union_table
 GROUP BY count_type;

此解决方案的缺点是，$maxImageWidth
和$maxImageHeight
变量分别使用了4次（和$imgId
一次）。如果您正在准备如图所示的语句（将值嵌入表示SQL的字符串中），那么还不错。如果您正在使用占位符，则可能需要占位符的命名方案（：img\u ht
，：img\u wd
，：img\u id
（或至少：1
，：2
，：3
）来代替？
占位符），以便在EXECUTE语句中只传递每个值一次。不过，这种能力取决于您的DBMS；MySQL是许多不支持此功能的DBMS之一。
在主映像和次映像表中是否有primaryId索引？如果是，那么应该将where子句推到内部，以便可以使用索引
SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images WHERE imgId = $imgId AND imgWidth != $maxImageWidth AND imgHeight = $maxImageHeight 
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images WHERE primaryId = $imgId AND imgWidth != $maxImageWidth AND imgHeight = $maxImageHeight
) AS union_table

否则将进行完整的表扫描以查找imgId，因为union_表是由Mysql创建的临时表，没有任何索引。
在主映像和次映像表中是否有primaryId索引？如果是，那么应该将where子句推到内部，以便可以使用索引
SElECT COUNT(*) AS imgCount FROM (
    SELECT imgHeight, imgWidth, imgId AS primaryId FROM primary_images WHERE imgId = $imgId AND imgWidth != $maxImageWidth AND imgHeight = $maxImageHeight 
    UNION ALL 
    SELECT imgHeight, imgWidth, primaryId FROM secondary_images WHERE primaryId = $imgId AND imgWidth != $maxImageWidth AND imgHeight = $maxImageHeight
) AS union_table

否则将进行完整的表扫描以查找imgId，因为union_表是由Mysql创建的临时表，没有任何索引。
谢谢您的回答。好奇的是，这会给我提供三种不同的价值观吗？我想我应该在问题中提到这一点。我需要知道所有三个WHERE子句的不同计数值。另外，我有点不确定为什么在WHERE子句中，下面的行和（$imgId AND
中有$imgId
？不，这只会提供1个值，如果您想要3个不同的值，请稍等片刻，我为您撰写一个答案。此外，您可能注意到，我编辑了“$imgId AND”部分out@stefmikhail您应该循环抛出结果集。实际上有三个数组：）@stefmikhail是的，但是您应该与mysql\u fetch\u assoc
：）@stefmikhail一起使用循环，而（$row=mysql\u fetch\u assoc（$result））{$cnt[$row['COL1']=$row['imgCount']；}
。现在您将有一个包含三个值的数组：$cnt['ALL EQUAL']
，$cnt['WIDTH EQUAL']
和$cnt['HEIGHT EQUAL']
。谢谢您的回答。好奇的是，这会给我提供三种不同的价值观吗？我想我应该在问题中提到这一点。我需要知道所有三个WHERE子句的不同计数值。另外，我有点不确定为什么在WHERE子句中，下面的行和（$imgId AND
中有$imgId
？不，这只会提供1个值，如果您想要3个不同的值，请稍等片刻，我为您撰写一个答案。此外，您可能注意到，我编辑了“$imgId AND”部分out@stefmikhail您应该循环抛出结果集。实际上有三个数组：）@stefmikhail是的，但是您应该与mysql\u fetch\u assoc
：）@stefmikhail一起使用循环，而（$row=mysql\u fetch\u assoc（$result））{$cnt[$row['COL1']=$row['imgCount']；}
。现在您将有一个包含三个值的数组：$cnt['ALL EQUAL']
，$cnt['WIDTH EQUAL']
和$cnt['HEIGHT EQUAL']
=
和
在MySQL中是等价的，它们之间没有区别。=
和
在MySQL中是等价的，它们之间没有区别。我将对此进行测试。只是想知道，工会不会自动分组吗？还是我在想什么