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使用 PageHelper 插件分页查询很慢？一招帮你搞定！
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描述2
原因select count(*) from ("原来的查询sql,相当于多查了一遍") userSELECT count(0)
FROM (SELECT V.*,B.TypeName AS TravelTypeName
FROM (SELECT A.PKID, A.ApplyOrderNo FROM t1 AS A
LEFT JOIN t2 AS P
ON P.ApplyOrderNo = A.ApplyOrderNo
LEFT JOIN t3 AS T
ON A.UserCode = T.UserCode ) AS V
LEFT JOIN t4 AS B
ON V.TravelCode = B.TypeCode AND V.UserCode = B.UserCode AND B.Isdel = 0）
SELECT V.*,B.TypeName AS TravelTypeName
FROM (SELECT A.PKID, A.ApplyOrderNo FROM t1 AS A
LEFT JOIN t2 AS P
ON P.ApplyOrderNo = A.ApplyOrderNo
LEFT JOIN t3 AS T
ON A.UserCode = T.UserCode ) AS V
LEFT JOIN t4 AS B
ON V.TravelCode = B.TypeCode AND V.UserCode = B.UserCode AND B.Isdel = 03
优化方案Page<Map<String, Object>> getOrderInfo(Map<String, Integer> map);Long getOrderInfo_COUNT();<select id="getOrderInfo" resultType="Long" useCache="false">
SELECT V.*,B.TypeName AS TravelTypeName
FROM (SELECT A.PKID, A.ApplyOrderNo FROM t1 AS A
LEFT JOIN t2 AS P
ON P.ApplyOrderNo = A.ApplyOrderNo
LEFT JOIN t3 AS T
ON A.UserCode = T.UserCode ) AS V
LEFT JOIN t4 AS B
ON V.TravelCode = B.TypeCode AND V.UserCode = B.UserCode AND B.Isdel = 0
</select>
<select id="getOrderInfo_COUNT" resultType="Long" useCache="false">
SELECT
COUNT(1)
FROM t1
</select>3
总结4
解决办法
【福利】2023 高薪课程，全面来袭（视频+笔记+源码）
【福利】2023 高薪课程，全面来袭（视频+笔记+源码）
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