某银行做校园卡缴费的测试过程中,发现成功缴费时间很长,大约需要75秒左右,原因分析:在做校园卡缴费的时候,首先是从数据库中查询到需要缴费的费项,然后再对该费项进行缴费,缴费成功后修改相应的状态,交易完成后,查看日志,发现下面的查询语句执行时间很长,在数据库中执行时间大约33.782 secs.秒
低效SQL(耗时:33.782 secs.):
代码如下 | 复制代码 |
SELECT DISTINCT hmc.bjbh, hmc.pxjgid, hmc.bjmc, csb.tjxbt, hmc.pxlx, hmc.bjrs, hmc.bjsfjs, csb.xzqhdm, hmc.shyj, hmc.kbrq FROM px_bjhmc hmc, ldlsc_xtcsb csb, px_xyhmc c WHERE hmc.pxjgid = csb.dwbh AND hmc.pxjgid = c.pxjgid AND hmc.shyj = '1' ---www.111cn.net |
优化方案一(耗时:6.485 secs.):
代码如下 | 复制代码 |
SELECT DISTINCT hmc.bjbh, hmc.pxjgid, hmc.bjmc, csb.tjxbt, hmc.pxlx, hmc.bjrs, hmc.bjsfjs, csb.xzqhdm, hmc.shyj, hmc.kbrq FROM px_bjhmc hmc, ldlsc_xtcsb csb, px_xyhmc c WHERE hmc.pxjgid = csb.dwbh AND hmc.pxjgid = c.pxjgid AND csb.dwbh = c.pxjgid ----在这里 AND hmc.shyj = '1' AND hmc.bjsfjs = '1' AND c.pxsfjs = '1' AND hmc.jyrq >= '20130505000000' AND hmc.jyrq <= '20140102235959' AND hmc.pxjgid = '00000000000020' |
低效SQL(耗时:33.782 secs.):
代码如下 | 复制代码 |
SELECT DISTINCT hmc.bjbh, hmc.pxjgid, hmc.bjmc, csb.tjxbt, hmc.pxlx, hmc.bjrs, hmc.bjsfjs, csb.xzqhdm, hmc.shyj, hmc.kbrq FROM px_bjhmc hmc, ldlsc_xtcsb csb, px_xyhmc c WHERE hmc.pxjgid = csb.dwbh AND hmc.pxjgid = c.pxjgid AND hmc.shyj = '1' AND hmc.bjsfjs = '1' AND c.pxsfjs = '1' AND hmc.jyrq >= '20130505000000' AND hmc.jyrq <= '20140102235959' AND hmc.pxjgid = '00000000000020' |
优化方案二(耗时:0.031 secs.):
代码如下 | 复制代码 |
SELECT DISTINCT hmc.bjbh, hmc.pxjgid, hmc.bjmc, csb.tjxbt, hmc.pxlx, hmc.bjrs, hmc.bjsfjs, csb.xzqhdm, hmc.shyj, hmc.kbrq FROM px_bjhmc hmc, ldlsc_xtcsb csb WHERE hmc.pxjgid = csb.dwbh AND EXISTS (SELECT 1 FROM px_xyhmc c WHERE hmc.pxjgid = c.pxjgid AND c.pxsfjs = '1') AND hmc.shyj = '1' AND hmc.bjsfjs = '1' AND hmc.jyrq >= '20130505000000' |
•多表同时关联:a.id = b.id, a.id = c.id, b.id = c.id;
•多表联接查询时,联少不联多,避免笛卡尔积操作;
•当一个表仅作为检索条件时,避免联接查询,多数情况下用Exists语句进行优化;
时间: 2024-12-24 08:50:26