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一，oracle中nvl()函數
NVL（表達式1，表達式2）
如果表達式1為空值，NVL返回值為表達式2的值，否則返回表達式1的值。該函數的目的是把一個空值（null）轉換成一個實際的值。其表達式的值可以是數字型、字符型和日期型。但是表達式1和表達式2的數據類型必須為同一個類型。
二，oracle數據庫中sql語句中with as 的用法
相當於建了個e臨時表
with e as (select * from scott.emp e where e.empno=7499)
select * from e;
三，Oracle中的group by問題
這條查詢語句最后的group by在oracle數據庫中可以那樣寫，但是在gbase中不可以，因為上面已經把happen_time這個時間起了別名了，oracle數據庫中，group by后面不能跟別名，gbase只能寫別名，gbase只認識上面已經起了別名的名字。
適配gbase正確語句：
select to_char(happen_time,'yyyy-MM-dd') as happen_date,count(1) as cn from dy_work_reminder a
where a.dm_entry_person = '1'
and to_char(a.happen_time,'yyyy-MM')='2019-06'
and a.yxbz='Y' group by happen_date
四，trunc()的用法
在oracle中，trunc()的用法
1.select trunc(sysdate) from dual --2011-3-18 今天的日期為2011-3-18
2.select trunc(sysdate, 'mm') from dual --2011-3-1 返回當月第一天.
3.select trunc(sysdate,'yy') from dual --2011-1-1 返回當年第一天
4.select trunc(sysdate,'dd') from dual --2011-3-18 返回當前年月日
5.select trunc(sysdate,'yyyy') from dual --2011-1-1 返回當年第一天
6.select trunc(sysdate,'d') from dual --2011-3-13 (星期天)返回當前星期的第一天
7.select trunc(sysdate, 'hh') from dual --2011-3-18 14:00:00 當前時間為14:41
8.select trunc(sysdate, 'mi') from dual --2011-3-18 14:41:00 TRUNC()函數沒有秒的精確
Oracle獲取當前月份的第一天的sql語句
select trunc(sysdate, 'mm') from dual;
Gbase獲取當前月份的第一天的sql語句
select trunc(current,'month') from sysmaster:sysdual;
注意：oracle中的dual是虛擬表，而gbase中的sysmaster:sysdual表同樣是gbase的虛表。
五，批量插入
oracle批量插入
接口
int insterZqyjList(List<YzsylgkZqyj> zqyjList);
xml
<insert id="insterZqyjList" parameterType="List">
insert into YZSYLGK_ZQYJ (YJ_ID, ID, YJ_NR,
TCR_NAME, TCRDW, CREATEDATE,
MODIFYDATE, USER_ID, ORG_ID
) select a.* from(
<foreach collection="list" item="item" index="index" separator="union" open="(" close=")">
select #{item.yjId,jdbcType=VARCHAR}, #{item.id,jdbcType=VARCHAR}, #{item.yjNr,jdbcType=VARCHAR},
#{item.tcrName,jdbcType=VARCHAR}, #{item.tcrdw,jdbcType=VARCHAR}, #{item.createdate,jdbcType=TIMESTAMP},
#{item.modifydate,jdbcType=TIMESTAMP}, #{item.userId,jdbcType=VARCHAR}, #{item.orgId,jdbcType=VARCHAR} from dual
</foreach>
)a
</insert>
適配GBase寫法
<insert id="insterZqyjList" parameterType="List" databaseId="gbase">
insert into YZSYLGK_ZQYJ (YJ_ID, ID, YJ_NR,
TCR_NAME, TCRDW, CREATEDATE,
MODIFYDATE, USER_ID, ORG_ID
) select a.* from(
<foreach collection="list" item="item" index="index" separator="union">
select '${item.yjId}' as YJ_ID, '${item.id}' as ID, '${item.yjNr}' as YJ_NR,
'${item.tcrName}'as TCR_NAME, '${item.tcrdw}' as TCRDW,
<choose>
<when test="item.createdate ='' or item.createdate=null">
get_datetime('${item.createdate}') as CREATEDATE
</when>
<otherwise>
'' as CREATEDATE,
</otherwise>
</choose>
<choose>
<when test="item.modifydate ='' or item.modifydate=null">
get_datetime('${item.modifydate}') as MODIFYDATE,
</when>
<otherwise>
'' as MODIFYDATE,
</otherwise>
</choose>
'${item.userId}' as USER_ID, '${item.orgId}' as ORG_ID from dual
</foreach>
)a
</insert>
Choose / when / otherwise是為了保證入參不為空，如果為空則前后插入的數量不匹配報錯，如果為空則返回空字符串。
（知識點）Oracle批量更新
xml寫法如下
<update id="updateBatch" parameterType="java.util.List">
<foreach collection="list" item="item" index="index" open="begin" close=";end;" separator=";">
update T_CITY_INDEX t
set
t.city_name= #{item.cityName,jdbcType=VARCHAR} ,
t.district_name= #{item.districtName,jdbcType=VARCHAR} ,
where t.id = #{item.id,jdbcType=NUMERIC}
</foreach>
</update>
六，Oracle數據庫和GBase數據庫的差異
Oracle數據庫和GBase數據庫的差異如下：
6.1 <=
Oracle：#{starttime}<=t.audit
Gbase：#{starttime}year to function(5)<=t.audit
6.2、groupby
Oracle：group by to_char(sysdate,’yyyy-MM’)
Gbase：group by 后面不能直接跟to_char(sysdate,’yyyy-MM’)，需要先給
to_char起一個別名例如a，然后group b ya
6.3、with別名as
Oracle：在oracle數據庫中可以使用with別名as的用法，相當於建了一張臨時
表，例如
with tmp as(select * from test)
Selecta.test1,b.test2 from try a,tmp b where a.id=b.id
GBase：在GBase中不可以使用with別名as的用法，只能這樣寫
Selecta.test1,b.test2 from try a,(select * from test) b where a.id=b.id
6.4、to_char()
Oracle：select to_char(a.id) id from...
GBase：select ‘a.id’ id from...
6.5、批量插入
Oracle：在foreach標簽中接收yjId參數時是這樣接收的
{item.yjId,jdbcType=VARCHAR}
GBase：在foreach標簽中接受yjId參數時是這樣接收的
'${item.yjId}' as YJ_ID
注意：這里有一對單引號
6.6、sysdate和current
Oracle：查詢當前時間使用sysdate Select sysdate from dual;
GBase：查詢當前時間使用current Select current from sysmaster:sysdual;
（sysmaster:sysdual是GBase的虛表）
6.7、多表連接
Oracle：可以使用（+）來連接各個表
GBase：不支持（+）用法，可以使用左連接leftjoin..on..來作連接查詢。
6.8、當前時間now()和current
Oracle：小於當前時間的寫法：<=now()
GBase：小於當前時間的寫法：<=current
6.9、trunc()函數
Oracle：trunc(sysdate)獲取當前的日期
GBase：trunc(current year to fraction(5))
七，多表連接
oracle的寫法
select a.title,a.begintime,null as END_DATE ,a.compere,a.org_id,a.typeid,a.id,a.xindeandbiji,a.meeting_type,c.org_name,le.STATE,
le.xdbgid,bj.STATE bjzt,bj.xdbgid bjid,d.ztdrlx,d.themetype,
b.user_id,a.recuserid,a.hyjy_state,null as bmzt,null as fczs_id
from meeting_main a,meeting_user b,g_organ c,meeting_ztdr d,LEARNING_NOTES le,LEARNING_NOTES bj
where a.org_id=c.org_id
and a.id = b.mainid
and a.id = d.id
and a.id = le.PROJECTID(+)
and a.id = bj.PROJECTID(+)
and le.type(+) = '0'
and bj.type(+) = '1'
and b.user_id = #{userId,jdbcType=VARCHAR}
gbase的（+）不適配，需要統統都改成left join 表名 on 條件
gbase的寫法
select a.title,a.begintime,null as END_DATE ,a.compere,a.org_id,a.typeid,a.id,a.xindeandbiji,a.meeting_type,c.org_name,le.STATE,
le.xdbgid,bj.STATE bjzt,bj.xdbgid bjid,d.ztdrlx,d.themetype,
b.user_id,a.recuserid,a.hyjy_state,null as bmzt,null as fczs_id
from
meeting_main a left join meeting_user b on
a.id = b.mainid left join g_organ c on
a.org_id = c.org_id left join meeting_ztdr d on
a.id = d.id left join LEARNING_NOTES le on
a.id = le.PROJECTID left join LEARNING_NOTES bj on
a.id = bj.PROJECTID
where
b.user_id = '1'
八，XMLAGG函數
oracle的寫法
select substr(aorgid,0,length(aorgid)-1) aorgid,substr(aorg_name,0,length(aorg_name)-1) aorg_name from (
select XMLAGG(XMLELEMENT(E,orgid || ',')).EXTRACT('//text()').getclobval() aorgid,
XMLAGG(XMLELEMENT(E,org.org_name || ',')).EXTRACT('//text()').getclobval() aorg_name
from exam_exam_org b,g_organ org where b.orgid=org.org_id
and b.exid=#{exid,jdbcType=VARCHAR}
) a
gbase的寫法
select substr(aorgid,0,length(aorgid)-1) aorgid,substr(aorg_name,0,length(aorg_name)-1) aorg_name from (
select WM_concat(orgid) aorgid,
WM_concat(org.org_name) aorg_name
from exam_exam_org b,g_organ org where b.orgid=org.org_id
and b.exid=#{exid,jdbcType=VARCHAR}
) a
九，to_char()用法
oracle的寫法
SELECT
to_char(a.id) id,
a.SCOREPROJECT,
b.USERID,
to_char(b.score) score,
to_char(a.SCORESUM) scoresum
FROM
score_ruler a,
( SELECT USERID, SCOREPROJECTID, sum( score ) score FROM SCORE_LOG WHERE USERID = #{userid,jdbcType=VARCHAR} GROUP BY USERID, SCOREPROJECTID ) b
WHERE
a.ID = b.SCOREPROJECTID ( + )
gbase的寫法
SELECT
'a.id' id,
a.SCOREPROJECT,
b.USERID,
'b.score' score,
'a.SCORESUM' scoresum
FROM
score_ruler a,
( SELECT USERID, SCOREPROJECTID, sum( score ) score FROM SCORE_LOG WHERE USERID = #{userid,jdbcType=VARCHAR} GROUP BY USERID, SCOREPROJECTID ) b
WHERE
a.ID = b.SCOREPROJECTID ( + )
十，查看當前月份trunc( )函數
oracle的寫法
select trunc(sysdate,'mm') from dual;
gbase的寫法
select trunc(current year to fraction(5),'month') from dual;
十一，group by
oracle寫法
<select id="selectPartyAge" parameterType="java.lang.String"
resultType="cn.com.qianlong.light.vo.dy.DyTjCxVo">
SELECT BB.name,nvl(AA.value,'0')value
FROM
(SELECT
CASE
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19490930' THEN '1949之前'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19491001'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19660430' THEN '1949~1966'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19660501'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19761031' THEN '1966~1976'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19761101'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19781231' THEN '1976~1978'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19790101'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '20021031' THEN '1979~2002'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '20021101'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '20121031' THEN '2002~2012'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '20121101' THEN '2012之后'
END as name , COUNT(z.ybdybeginDate) AS value
FROM (
SELECT a.user_id, a.ybdybeginDate, a.partyorganId FROM DY_INFO a,G_ORGAN b
where
a.PARTYORGANID like CONCAT('%',CONCAT(#{partyorganid,jdbcType=VARCHAR},'%'))
and a.status IN (1,4)
AND a.userType IN (4, 5)
AND
a.PARTYORGANID=b.ORG_ID
and
b.VALIDFLAG = 1
) z
GROUP BY CASE
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19490930' THEN '1949之前'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19491001'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19660430' THEN '1949~1966'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19660501'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19761031' THEN '1966~1976'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19761101'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19781231' THEN '1976~1978'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19790101'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '20021031' THEN '1979~2002'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '20021101'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '20121031' THEN '2002~2012'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '20121101' THEN '2012之后'
END
)AA RIGHT JOIN (
select '1949之前' as name, '1' as xh from dual
union
select '1949~1966' as name, '2' as xh from dual
union
select '1966~1976' as name, '3' as xh from dual
union
select '1976~1978' as name, '4' as xh from dual
union
select '1979~2002' as name, '5' as xh from dual
union
select '2002~2012' as name, '6' as xh from dual
union
select '2012之后' as name, '7' as xh from dual
)BB on AA.name=BB.name
ORDER BY BB.xh
</select>
gbase寫法
<select id="selectPartyAge" parameterType="java.lang.String"
resultType="cn.com.qianlong.light.vo.dy.DyTjCxVo">
SELECT BB.name,nvl(AA.value,'0')value
FROM
(SELECT
CASE
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19490930' THEN '1949之前'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19491001'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19660430' THEN '1949~1966'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19660501'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19761031' THEN '1966~1976'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19761101'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '19781231' THEN '1976~1978'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '19790101'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '20021031' THEN '1979~2002'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '20021101'
AND TO_CHAR(z.ybdybeginDate,'YYYYMMDD') <= '20121031' THEN '2002~2012'
WHEN TO_CHAR(z.ybdybeginDate,'YYYYMMDD') >= '20121101' THEN '2012之后'
END as dd , COUNT(z.ybdybeginDate) AS value
FROM (
SELECT a.user_id, a.ybdybeginDate, a.partyorganId FROM DY_INFO a,G_ORGAN b
where
a.PARTYORGANID like CONCAT('%',CONCAT(#{partyorganid,jdbcType=VARCHAR},'%'))
and a.status IN (1,4)
AND a.userType IN (4, 5)
AND
a.PARTYORGANID=b.ORG_ID
and
b.VALIDFLAG = 1
) z
GROUP BY dd
)AA RIGHT JOIN (
select '1949之前' as name, '1' as xh from dual
union
select '1949~1966' as name, '2' as xh from dual
union
select '1966~1976' as name, '3' as xh from dual
union
select '1976~1978' as name, '4' as xh from dual
union
select '1979~2002' as name, '5' as xh from dual
union
select '2002~2012' as name, '6' as xh from dual
union
select '2012之后' as name, '7' as xh from dual
)BB on AA.name=BB.name
ORDER BY BB.xh
</select>
十二，查看當前星期的星期一的日期
oracle寫法
select trunc(sysdate,'iw') from dual;
gbase寫法
select trunc(current,'day')+1 from dual;
參考gbase官方文檔
