1. 先說刪除吧，因?yàn)閯偢懔恕?/h3>
刪除緩慢的原因：主要是約束的問題。（數(shù)據(jù)庫在有約束的時(shí)候，進(jìn)行操作，會(huì)根據(jù)約束對(duì)相關(guān)表進(jìn)行驗(yàn)證，可想而知，20W的數(shù)據(jù)驗(yàn)證要耗費(fèi)多久的時(shí)間）。其次就是sql的編寫。（sql如果查詢中包含子查詢等的可以優(yōu)化的where會(huì)影響匹配的速度查詢的話就不多逼逼了>）。索引的問題 請(qǐng)看下面的 補(bǔ)充部分
具體解決方法：
ALTER TABLE tableName DISABLE TRIGGER ALL;
delete 目標(biāo)語句
ALTER TABLE tableName ENABLE TRIGGER ALL;
2. 更新，原因和刪除大體一致，這里主要描述一下自己遇到的問題。
利用mybatis批量更新，第一張圖是原本的批量更新的寫法，發(fā)現(xiàn)在本地還可以的但是放在服務(wù)器會(huì)由于時(shí)間太久出現(xiàn)IO錯(cuò)誤。
后來換成第二張圖的方式來更新。當(dāng)然也可以java代碼for循環(huán)來單條更新來達(dá)到批量的目的。（對(duì)于這三種方式，第二種最快）
update id="batchUpdate2" parameterType="java.util.List">
UPDATE lt_dzheinfo
trim prefix="set" suffixOverrides=",">
trim prefix="dzzhao =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then #{reader.readerBarcode}
/foreach>
/trim>
trim prefix="xming =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then #{reader.readerName}
/foreach>
/trim>
trim prefix="ztai =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then #{reader.readerState}
/foreach>
/trim>
trim prefix="mima =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then #{reader.readerPsw}
/foreach>
/trim>
trim prefix="dzlxid =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then #{reader.readerType}
/foreach>
/trim>
trim prefix="zjlx =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then #{reader.identityType}
/foreach>
/trim>
trim prefix="zjhma =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then #{reader.identityId}
/foreach>
/trim>
trim prefix="qyrqi =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then TO_TIMESTAMP(#{reader.enableDate}, 'YYYY-MM-DD HH24:MI:SS')
/foreach>
/trim>
trim prefix="jzrqi =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then TO_TIMESTAMP(#{reader.disableDate}, 'YYYY-MM-DD HH24:MI:SS')
/foreach>
/trim>
trim prefix="libid =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then #{reader.readerOfLibCode}
/foreach>
/trim>
trim prefix="xingbie =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then
choose>
when test="reader.readerSex=='男'.toString()">
true
/when>
otherwise>
false
/otherwise>
/choose>
/foreach>
/trim>
trim prefix="userid =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then #{reader.readerOperatorId}
/foreach>
/trim>
trim prefix="beizhu =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then #{reader.readerRemark}
/foreach>
/trim>
trim prefix="bzrqi =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then TO_TIMESTAMP(#{reader.enableDate}, 'YYYY-MM-DD HH24:MI:SS')
/foreach>
/trim>
trim prefix="optime =case" suffix="end,">
foreach collection="list" item="reader" index="index">
when dzid=#{reader.readerId} then TO_TIMESTAMP(#{reader.enableDate}, 'YYYY-MM-DD HH24:MI:SS')
/foreach>
/trim>
/trim>
where dzid in
foreach collection="list" index="index" item="reader" separator="," open="(" close=")">
#{reader.readerId}
/foreach>
/update>
update id="batchUpdate" parameterType="java.util.List">
foreach collection="list" index="index" item="reader" separator=";">
UPDATE lt_dzheinfo SET
dzzhao = #{reader.readerBarcode},
xming = #{reader.readerName},
ztai = #{reader.readerState},
mima = #{reader.readerPsw},
dzlxid = #{reader.readerType},
zjlx = #{reader.identityType},
zjhma = #{reader.identityId},
qyrqi = TO_TIMESTAMP(#{reader.enableDate}, 'YYYY-MM-DD HH24:MI:SS'),
jzrqi = TO_TIMESTAMP(#{reader.disableDate}, 'YYYY-MM-DD HH24:MI:SS'),
libid = #{reader.readerOfLibCode},
xingbie =
choose>
when test="reader.readerSex=='男'.toString()">
true
/when>
otherwise>
false
/otherwise>
/choose>,
userid = #{reader.readerOperatorId},
beizhu = #{reader.readerRemark},
bzrqi = TO_TIMESTAMP(#{reader.enableDate}, 'YYYY-MM-DD HH24:MI:SS'),
optime = TO_TIMESTAMP(#{reader.enableDate}, 'YYYY-MM-DD HH24:MI:SS')
where>
dzid = #{reader.readerId}
/where>
/foreach>
/update>
補(bǔ)充：數(shù)據(jù)庫突然變慢...索引作怪！
本人在最近發(fā)現(xiàn)，有些比容量較大的SQL數(shù)據(jù)庫，在使用一段時(shí)間后，會(huì)突然變很慢很慢。特別體現(xiàn)在一些經(jīng)常進(jìn)行操作及查詢的大表中。經(jīng)過深入研究，這一般是索引的問題！如果把此表的索引重建一次，問題即可解決。
為更好地解決此問題，建意在SQL中新建一個(gè)數(shù)據(jù)庫維護(hù)計(jì)劃，選中“重新組織數(shù)據(jù)各索引頁”選項(xiàng)，并設(shè)置每天運(yùn)行一次。
/*
刷新數(shù)據(jù)庫視圖.sql
*/
ALTER PROC P_RefreshView
as
DECLARE @vName sysname
DECLARE refresh_cursor CURSOR FOR
SELECT Name from sysobjects WHERE xtype = 'V' order by crdate
FOR READ ONLY
OPEN refresh_cursor
FETCH NEXT FROM refresh_cursor
INTO @vName
WHILE @@FETCH_STATUS = 0
BEGIN
--刷新指定視圖的元數(shù)據(jù)。由于視圖所依賴的基礎(chǔ)對(duì)象的更改，視圖的持久元數(shù)據(jù)會(huì)過期。
exec sp_refreshview @vName
PRINT '視圖' + @vName + '已更新'
FETCH NEXT FROM refresh_cursor
INTO @vName
END
CLOSE refresh_cursor
DEALLOCATE refresh_cursor
GO
SET QUOTED_IDENTIFIER OFF
GO
SET ANSI_NULLS ON
GO
以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。如有錯(cuò)誤或未考慮完全的地方，望不吝賜教。
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