Question

我正在尝试对查询进行性能调整，并且需要帮助

我们需要根据多种因素在网站上提取数据，从而导致复杂的查询工作正常，但价格昂贵。我们拥有所有正确的索引。

我遇到的问题是在查询中删除DISTINCT的使用（这似乎是瓶颈）。

我不是SQL专家，我想我已经尽力了。

任何有助于简化此查询并删除DISTINCT（或不使用GROUP BY）的帮助将不胜感激。谢谢。

SELECT DISTINCT  t2.PK  
FROM categories t0 
    JOIN cat2catrel t1 ON  t1.SourcePK  =  t0.PK  
    JOIN categories t2 ON  t1.TargetPK  =  t2.PK  
    JOIN cat2catrel t3 ON  t3.SourcePK  =  t2.PK  
    JOIN categories t4 ON  t3.TargetPK  =  t4.PK  
    JOIN cat2prodrel t5 ON  t5.SourcePK = t4.PK  
    JOIN products t6 ON  t5.TargetPK  =  t6.PK  
    JOIN stocklevels t7 ON  t7.productcode  =  t6.code  
    JOIN relativeinventory t8 ON  t7.p_inventory  =  t8.PK  
    JOIN warehouses t9 ON  t7.warehouse  =  t9.PK  
    JOIN pos2warehouserel t10 ON  t10.TargetPK  =  t9.PK  
    JOIN pos2warehouserel t10 ON  t10.TargetPK  =  t9.PK  
    JOIN pointofservice item_t11 ON  t10.SourcePK  =  t11.PK  
    WHERE  ( t0.code  = 'code' 
        AND  t8.nventorystatus  IN (1111) 
        AND  t11.name  = 'ABC') 
        AND ((t0.TypePkString IN  (1, 2, 3, 4)  
        AND (( t0.catalogversion  IN (1, 2, 3)))  
        AND t1.TypePkString=1000 
        AND t2.TypePkString IN  (1, 2, 3, 4)  
        AND (( t2.catalogversion  IN (1, 2)))  
        AND t3.TypePkString=300  
        AND t4.TypePkString IN  (6, 7, 8)  
        AND (( t4.catalogversion  IN (5, 6)))  
        AND t5.TypePkString=500 
        AND t6.TypePkString=600 
        AND t7.TypePkString=200  
        AND t8.TypePkString=700 
        AND t9.TypePkString IN  (3, 7)  
        AND t10.TypePkString=900  
        AND t11.TypePkString=750 ));

当前，此查询工作正常，并提供了我想要的结果。我只是不想使用DISTINCT或GROUP BY而仍然获得独特的结果。

数据库：MySQL 6.3

Answer 1

您仅选择t2.pk，它似乎是类别表中的主键。如果这是正确的话，那么您的Join会产生重复。通常，在这种情况下摆脱DISTINCT的最简单解决方案是从要选择的表开始，并确保将INNER JOINING绑定到该表。但是，看来您实际上已经在执行此操作了，但是您正在复制联接...即t0和t2是同一张表，这对我来说是一个很大的危险信号。尝试这样的事情：

SELECT t0.PK  
FROM categories t0 
    INNER JOIN cat2catrel t1 ON  t1.SourcePK  =  t0.PK AND t1.TargetPK = t0.PK
    INNER JOIN cat2catrel t3 ON  t3.SourcePK  =  t0.PK  
    INNER JOIN categories t4 ON  t3.TargetPK  =  t4.PK  
    INNER JOIN cat2prodrel t5 ON  t5.SourcePK = t4.PK  
    INNER JOIN products t6 ON  t5.TargetPK  =  t6.PK  
    INNER JOIN stocklevels t7 ON  t7.productcode  =  t6.code  
    INNER JOIN relativeinventory t8 ON  t7.p_inventory  =  t8.PK  
    INNER JOIN warehouses t9 ON  t7.warehouse  =  t9.PK  
    INNER JOIN pos2warehouserel t10 ON  t10.TargetPK  =  t9.PK  
    INNER JOIN pos2warehouserel t10 ON  t10.TargetPK  =  t9.PK  
    INNER JOIN pointofservice item_t11 ON  t10.SourcePK  =  t11.PK  
    WHERE  ( t0.code  = 'code' 
        AND  t8.nventorystatus  IN (1111) 
        AND  t11.name  = 'ABC') 
        AND ((t0.TypePkString IN  (1, 2, 3, 4)  
        AND (( t0.catalogversion  IN (1, 2, 3)))  
        AND t1.TypePkString=1000 
        AND t2.TypePkString IN  (1, 2, 3, 4)  
        AND (( t2.catalogversion  IN (1, 2)))  
        AND t3.TypePkString=300  
        AND t4.TypePkString IN  (6, 7, 8)  
        AND (( t4.catalogversion  IN (5, 6)))  
        AND t5.TypePkString=500 
        AND t6.TypePkString=600 
        AND t7.TypePkString=200  
        AND t8.TypePkString=700 
        AND t9.TypePkString IN  (3, 7)  
        AND t10.TypePkString=900  
        AND t11.TypePkString=750 ));

但是，我看到其他表格重复出现，例如“ pos2warehouserel”。 只应声明表一次并为其分配一个别名。

需要帮助来调整复杂的查询

1 个答案: