sql left join with where clause

The following is an example: ExampleTable Aid adate1 A12 A23 A3 Table B Bid bdate1 B12 B24 B4 Left join: Select * from a left join B on A. Aid = B. Bid First, retrieve all the data in Table A, and then add the data that matches table A and table B.In this case, the following information is taken: 1 A1 B12

SQL join left join query instance tutorial Table a: results and data StudentID workID store1 1 981 2 952 1 902 3 80 Table B: results and dataWorkID workName1 zuoye2 www. bKjia. c0m3 wenti The join left

From: http://www.cnblogs.com/kevinGaoblog/archive/2012/07/05/2577410.html--Execute in Query Analyzer:--Build Table Table1,table2:CREATE TABLE table1 (ID int,name varchar (10))CREATE TABLE table2 (ID int,score int)INSERT INTO table1 Select 1, ' Lee 'INSERT INTO Table1 Select 2, ' Zhang 'INSERT INTO table1 Select 4, ' Wang 'Insert INTO table2 Select 1,90Insert INTO table2 Select 2,100Insert INTO table2 select 3,70such as table-------------------------------------------------Table1 | Table2--------

Tags: SQL statementsProject requirements change, before writing a query SQL, need to modify, nausea for a long while did not change well, finally want to go, spell to spell (splicing SQL), the original directly to the inner join changed to the left

Tags: happy sharing feature for me select information from where BSPToday's work learning path is a database of small knowledge, at that time did not distinguish the why, hereby recorded share a sudden. As we all know, the tables of the database are all separate, but when we do a union query (multi-table query), we get the value returned by the database as if it were in a table, because the database generates a temporary table to return to the data information we want when we make a federated qu

Label:There are currently two tables, Sgroup and Sgroupuser, which are associated by Gkey, while the Sgroup table records the group, and the Sgroupuser record is the user in the group, so there is no data in the Sgroupuser. You need to use the left join to get the data: The LINQ syntax is as follows: var sg = ( from the dc.sgroup in dc.sgroupuser on G.gkey equals Gu.gkey into L

Left join returns records that include all the records in the left table and the equivalent of the junction fields in the right tableRight join returns records that include all records in the right table and the junction fields in the left tableINNER

exists is faster than not.difference between in and =Select name from student where name in (' Zhang ', ' Wang ', ' Li ', ' Zhao ');Select name from student where Name= ' Zhang ' or name= ' li ' orName= ' Wang ' or name= ' Zhao 'The result is the same.Left\right join is an external connection, inner join is an inner joinThe external connection has the main table and from the table, the main table is

Assume that the table structure is: user_info table: role_info table: to query some data from the user_info table and role_info table, for example, when logging on to the system, in addition to the login name and password, you can also query additional information, such as user permissions, which may be connected. Here we use the left join: the SQL statement is a

Tags: class color SQL arch null sel cross font divData preparation:Create TableT1 (Avarchar(Ten) not NULL, Bvarchar(Ten) not NULL, Ctinyint not NULL);Create TableT2 (Bvarchar(Ten) not NULL, Etinyint not NULL);Insert intoT1Values('A1','B1',5),('A1','B2',6),('A2','B3',8),('A2','B4', A);Insert intoT2Values('B1',3),('B2',7),('B3',Ten),('B3',2),('b5',2);Select * fromT1;Select * fromT2;Results:1 A B C2 ---------- ---------- ----3A1 B154A1 B265A2 B386A

Suppose the table's structure is: User_info table: Role_info table: To query some data from table user_info and table role_info, such as when you log on to the system, In addition to querying for information in terms of login names and passwords, additional information, such as user permissions, may be used to connect. Here use LEFT JOIN to connect: The SQL