how to write subquery in sql

1. subquery in SQL: When we are doing SQL questions, we are most afraid of complex query statements, because most of the time we need two or three subqueries for implementation, Most of the students are afraid of subqueries. I was confused by these questions, However, after doing a lot of such questions, we found that there are also some rules. We can sum up a se

cannot generate connection record (extra record) SelectE1.ename, E2.ename fromEMP E1 Left JoinEMP E2 on(E1.mgr=e2.empno); --full external link, the left and right side of the record can not generate connections to query out SelectENAME, Dname fromEMP E Full JoinDept D on(E.deptno=D.deptno); --From the connection, the same table will be different aliases, and then as two tables to use. The self-connection can be connected either inside or outside. SelectE1.ename,e2.ename fromEMP E1JoinEMP E2 on

Use [erp2015]go/****** object:storedprocedure [dbo]. [GetUser] Script date:03/14/2015 13:27:04 ******/set ansi_nulls ongoset quoted_identifier ongo--=============================== ==============--author:wangyanling--Create date:205-03-12--Description: Get customer information--================================ =============alter PROCEDURE [dbo]. [GetUser]--ADD the parameters for the stored procedure here@uname varchar ($) asbegin--SET NOCOUNT on added to prevent Extra result sets from--inter

Tags: conditional msi order top sum end tar Mon oneResult set of the first query Select* from( SelectC.msname,a.msid,c.msprice, C.msprice*count (A.MSID) asTotalmoney,sum (A.msamount) asTotalCount fromBillconsume a RIGHT join (SelectTop1Mstime asStarttime,getdate () asEndTime fromBillconsumewhereDateDiff (Dd,mstime,getdate ()) =0ORDER BY mstime ASC) b on a.mstime between B.starttime and B.endtime and a.msid!=0Left join Menus C on C.msid=a.msid GROUP by A.msid, C.msname,c.msprice) s A statement th

* Query two columns of data from two different tablesMake contact with the same column in the two tables through a subqueryExample: Query all students for Sname, CNO, and degree columns.Select (select Sname from Student where Student.sno=score.sno), Cno,degree from score--where sname is in the Student table, CNO and degree in the score table, where two tables have Student.sno=score.sno connections-- use a table with more data to query the main table, where score is the main tableSecond, aggrega

* fromEmpwhereEmpno not inch(SelectEmpno fromEmpwhereRowNumSize*(page- 1)) andRowNumsize; --sorting and then paging query --number of data after sorting (Efficiency row 2nd) Select * from(SelectRowNum RN, D.* from(Select * fromEmpOrder bySaldesc) d)whereRn> 5 andRn One; --Paging function: row_number function (1th efficiency row) SelectRow_number () Over(Order bySaldesc) RN, EMP.* fromEMP; --page Out Select * from(SelectRow_number () Over(Order bySaldesc) RN, EMP.* fromEm

Tags: SQL data performance Oracle--=========================--sql Base--subquery--=========================One, sub-queryA subquery is a query that is inside a select, UPDATE, or DELETE statementIi. classification of sub-queriesSingle-line subqueryReturns 0 rows or one rowMulti-row subqueriesReturn one or more rowsDole

A subquery is the embedding of a SQL Sever statement into another SQL Sever statement. The database engine performs a query operation on a subquery as a virtual table. Subqueries can be used as a table in a join statement, either as a value in a SELECT statement, as a SQL se

);}/** * Based on ID query Parkinfo * * @param ID * @return Parkinfo */@OverridePublic Parkinfo Getparkinfo (Integer ID) {Session session = Daohelp.getinstance (). GetSession (); Return (Parkinfo) Session.get (Parkinfo.class, id); }/** * Search by ID serviceitem * * @param ID * @return listPublic listSession session = Daohelp.getinstance (). GetSession ();String hql = "from Serviceitem where parkinfoid =:p arkid and status= ' 02 '";Query query = session.createquery (HQL); Query.setinteger ("Park

Dynamic Recently looked back at the SQL Server books, mainly on the SQL related subqueries and crosstab knowledge. The difference between a correlated subquery and a normal subquery is that the related subquery references the columns of the outer query. This ability to refer

Label:SELECT Info_key, Info_value, Info_status, Edit_timeF ROM (SELECT * from ' detail ' WHERE login = ' [e-mail protected] ' ORDER by Edit_time DESC) as AAAGROUP by Info_key Hope to realize the sub-query based on alias by Thinkphp, and finally refer to the following article to realize. Http://www.thinkphp.cn/update/122.html The following is the original text in the Help manual. (Search sub-query) New subquery support has been added since version

rows and columns: Mysql> SELECT * from Recuit, where (id,time) > (select Id,time from exam W Here id=1); +----+------------+-----------------+---------+--------+ | id | time | process | name | result | +----+------------+-----------------+---------+--------+ | 1 | 2016-08-31 | Wait for result | Baidu | 1 | | 2 | 2016-08-25 | haha | tengxun | 1 | | 3 | 2016-08-31 | Jiayou | Wangyi | 1 | | 9 | 2016-08-31 | Happy | W

belong to any of the list in the back of not, and the query does not return any values, unlike the expected result, the reason is that the non in clause is handling null values in SQL Server, the not as shown in Figure 2 The IN clause can actually be converted to a query as shown in 3. Figure 3: Equivalent conversions are possible for the NOT in clause In Figure 3, you can see that not in can be converted to a condition for each value of the unequa

Tags: problem SP c new SQL table BS r ROMIn a subquery, if you want to implement the following functions:Select Lib,count (*), select SUM (NEWSNO) from Table1 GROUP by LibFrom Tabel1 t1,table2 T2 where T1.newsno =t2.newsnoGroup by LibYou will be prompted that the subquery returns more than one value. "Error, meaning that a su