MySQL 动态生成多个 where 子句

Question

这样用户就可以选择他想要过滤列表的类别数量

当只选择一项时一切正常：

        SELECT SQL_CALC_FOUND_ROWS a.id, a.PAnr, b.family, b.articlenr, b.ratio, a.oiltype, a.oiltemp
        FROM testdata_test a, testdata_gear b
        WHERE a.id = b.test_id  AND b.family = 'R660' 
        ORDER BY a.PAnr desc
        LIMIT 0, 10

但是当用户添加更多时：

        SELECT SQL_CALC_FOUND_ROWS a.id, a.PAnr, b.family, b.articlenr, b.ratio, a.oiltype, a.oiltemp
        FROM testdata_test a, testdata_gear b
        WHERE a.id = b.test_id  AND b.family = 'R540' OR  b.family = 'R660' 
        ORDER BY a.PAnr desc
        LIMIT 0, 10

当不带 AND 部分的 table 约为 4000 时，我得到了大约 400 万次点击。如果用户选择另一个，则有大约 800 万次点击。我错过了什么？

Answer 1

您将 and 和 or 子句混合在一起而没有 ()，因此您实际上是运行:

WHERE ((a.id = b.test_id) AND (b.family = 'R540')) 
   OR (b.family = 'R660')

请注意 () 的位置。

你可能想要

WHERE (a.id = b.test_id) AND (b.family IN ('R540', 'R660'))

Answer 2

将您的查询更改为此，您的查询将不会运行 OR 语句如预期的那样，

SELECT SQL_CALC_FOUND_ROWS a.id, a.PAnr, b.family, b.articlenr, 
        b.ratio, a.oiltype, a.oiltemp
        FROM testdata_test a, testdata_gear b
        WHERE a.id = b.test_id  AND (b.family = 'R540' OR  b.family = 'R660')
        ORDER BY a.PAnr desc
        LIMIT 0, 10

或者

SELECT SQL_CALC_FOUND_ROWS a.id, a.PAnr, b.family, b.articlenr, 
        b.ratio, a.oiltype, a.oiltemp
        FROM testdata_test a, testdata_gear b
        WHERE a.id = b.test_id  AND b.family IN ('R540','R660')
        ORDER BY a.PAnr desc
        LIMIT 0, 10

MySQL 动态生成多个 where 子句

MySQL multiple where clauses generated dynamically

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