SQL语句PART8
PairWise subquery:
e.g.:
select * from wf_docsort where (ndocsortid,nmoduleinfoid) in (select ndocsortid, nmoduleinfoid from wf_docsort where instr(cname,'文')>0)
the above sql is the same function as:
select * from wf_docsort where ndocsortid = (select ndocsortid from wf_docsort where instr(cname,'xx')>0) and nmoduleinfoid = (select nmoduleinfoid from wf_docsort where instr(cname,'xx')>0)
A scalar subquery expression is a subquery that: returns exactly one column value from one row. Scalar subqueries can be used in: 1) The condition and expression part of DECODE and CASE 2) All clauses of SELECT except GROUP BY 3) The SET clause and WHERE clause of an UPDATE statement
e.g.:
select * from wf_docsort
results:
1 1 收文 SHOUWEN
2 1 发文 FAWEN
3 1 交办 JIAOBAN
4 2 值班报告 REPORT
5 3 督察督办 SUPERVISAL
6 2 值班快报 DAILYREPORT
7 2 我的事情 NOTIFY
8 4 提案 RESOLUTION
9 4 建议 SUGGESTION
select NDOCSORTID, NMODULEINFOID,CNAME,KEY,(
case when nmoduleinfoid=(
select nmoduleinfoid from wf_moduleinfo where nmoduleinfoid=1
) then 'JEAN1' else (case when nmoduleinfoid=(select nmoduleinfoid from wf_moduleinfo
&n
相关文档：
1. select replace(CA_SPELL,' ','') from hy_city_area 去除列中的所有空格
2. LTRIM（） 函数把字符串头部的空格去掉
3. RTRIM（） 函数把字符串尾部的空格去掉
4. select LOWER(replace(CA_SPELL,' ','')) f ......
第二十题：
怎么样抽取重复记录
表：
id name
--------
1 test1
2 test2
3 test3
4 test4
5 test5
6 test6
2 test2
3 test3
2 test2
6 test6
查出所有有重复记录的数据，用一句sql 来实现
create table D(
id varchar (20),
name varchar (20)
)
insert into D values('1','test1')
insert into D v ......
7、对象类型继承
对象类型实现允许我们创建一个基类型，或叫父类型，这种类型的属性或方法可以被另一个对象类型继承。然后可以创建一个子类型，或叫孩子类型，直接使用继承过来的属性或方法，或者用自己的属性和方法重写父类型的属性或方法。
INSTANTIABLE关键字表示我们可以从该类型中实例化或者创建对� ......
Differring Constraints:
Constraints can have the following attributes: DEFFERRABLE / NOT DEFFERRABLE, INITIALLY DEFFERRED / INITIALLY IMMEDIATE.
e.g.:
alter table dept2 add constraint dept2_id_pk primary key (department_id) deferrable initially deferred; // deferring constraint on creation. ......
Merge statement
function benefits: 1) provides the ability to conditionally update, insert or delete data into a database table. 2) performs an update if the row exists, and an insert if it is a new row. --> 1) avoids seperate updates, 2) increase performance and ease of use. 3) is useful in dat ......
