【mysql】mysql union查詢，實現分頁查詢和count統計

 

說明：

UNION 操作符用於合並兩個或多個 SELECT 語句的結果集。 請注意，UNION 內部的 SELECT 語句必須擁有相同數量的列。列也必須擁有相似的數據類型。同時，每條 SELECT 語句中的列的順序必須相同。否則會報錯。 union和 union all的關系和區別： 1.UNION ALL 命令和 UNION 命令幾乎是等效的，不過 UNION ALL 命令會列出所有的值。 2.即 ：union會對合並的兩個或多個查詢的結果集 進行 去重合並的操作。 union all則不會去重，只做合並，因此查出的結果集中 會有重復的記錄。

 

示例：

分頁查詢sql

( SELECT DISTINCT c.u_id, c.create_time FROM 表A a LEFT JOIN 表B b ON b.u_id = a.u_id AND b.yn = 1
        LEFT JOIN 表C c ON c.u_id = a.u_id AND c.yn = 1
        LEFT JOIN 表D d ON d.u_id = a.u_id AND d.yn = 1 
    WHERE
        1 = 1 
        AND a.yn = 1 
        AND b.vender_id IN ( 1 ) AND b.join_behavior = 1 
        AND b.store_join_type = 1 ) UNION ( SELECT DISTINCT c.u_id, c.create_time FROM 表A a LEFT JOIN 表B b ON b.u_id = a.u_id LEFT JOIN 表C c ON c.u_id = a.u_id LEFT JOIN 表D d ON d.u_id = a.u_id WHERE
        1 = 1 
        AND a.yn = 1 
        AND b.vender_id IN ( 1 ) AND b.join_behavior = 1 
        AND a.join_value IN ( 6 ) AND b.store_join_type = 2 ) ORDER BY create_time DESC LIMIT 0,200;

 

count統計sql:

select 
     COUNT(*) FROM ( ( SELECT DISTINCT c.u_id, c.create_time FROM 表A a LEFT JOIN 表B b ON b.u_id = a.u_id AND b.yn = 1
        LEFT JOIN 表C c ON c.u_id = a.u_id AND c.yn = 1
        LEFT JOIN 表D d ON d.u_id = a.u_id AND d.yn = 1 
    WHERE
        1 = 1 
        AND a.yn = 1 
        AND b.vender_id IN ( 1 ) AND b.join_behavior = 1 
        AND b.store_join_type = 1 ) UNION ( SELECT DISTINCT c.u_id, c.create_time FROM 表A a LEFT JOIN 表B b ON b.u_id = a.u_id AND b.yn = 1
        LEFT JOIN 表C c ON c.u_id = a.u_id AND c.yn = 1
        LEFT JOIN 表D d ON d.u_id = a.u_id AND d.yn = 1
    WHERE
        1 = 1 
        AND a.yn = 1 
        AND b.vender_id IN ( 1 ) AND b.join_behavior = 1 
        AND a.join_value IN ( 6 ) AND b.store_join_type = 2 ) ) AS temp