sql inner join example

For example A1 table 100W row A2 table 50W rowSelect A.* from A1 a where a.column1 in (select B.column1 from A2 b where b.column2= ' xxx ');Select A.* from A1 a where exists (select ' x ' from A2 b where b.column2=xxx and a.column1=b.column1);Select a.* from A1 a,a2 b where b.column2= ' xxx ' and a.column1=b.column1In cases where the result set (for example, only dozens of) of (select B.column from A2 b w

publisher equals book. publisher into publisherbooks select new {publisher = publisher. name, books = publisherbooks}; gridviewgroupjoin. databind (); AboveCodeIs the so-called "group connection ". It groups the books of each publishing house into publisherbooks and binds them together. This code is consistent with the running result of the following code. VaR x = from book in sampledata. Books Group book by book. Publisher into bookpublishers select new {publisher = bookpublishers. Key. Na

. Internal connection, usually use the most, the simplest equals number connection example: There are two tables, assuming that A and B are many-to-one relationship a LEFT join B the number of records connected to a table with the number of recordsA Right JoinThe number of records connected to B is equal to the number of records connected in A and B plus the number of records on the B no matchThis way, you

Label:Using EF's own small functions need to encounter inner join and group by combination of use and anonymous type of processing, search a lot, basically can not meet their own needs, so summed up also realized on their own write out, has been prepared to view and partner query Reference (General statement query does not say, the network search a lot) Statement query background (or not directly look at th

right connections, if the two sides can not match the conditions, then do not take out. 7.MySQL does not support external connections , and, accordingly, MySQL can use Union (union query) to isolate the left and right connections. 　　　The union query filters for duplicate rows, and union all does not filter for duplicate rows . 　　　union query, the number of SQL columns between the Union must be equal, the column name is the first

the right table in the row of the associated result set are null. 2. left join/right join/inner join Operation demonstration Table A records the following:AID aNum1 a200501112 a200501123 a200501134 a200501145 a20050115 Table B records the following:BID bName1 20060324012 20060324023 20060324034 20060324048 2006032408

list columns in the right table in the row of the associated result set are null. 2. Left join/right join/inner Join Operation demonstration Table A records the following:Aid anum1 a200501112 a200501123 a200501134 a200501145 a20050115 Table B records the following:Bid bname1 20060324012 20060324023 20060324034 20

Table A records the following: Aid anum 1 a20050111 2 a20050112 3 a20050113 4 a20050114 5 a20050115 Table B records the following: Bid bname 1 2006032401 2 2006032402 3 2006032403 4 2006032404 8 2006032408 The experiment is as follows: 1. Left join The SQL statement is as follows: Select * from Left join B On a. Aid = B. Bid The result is as follows: Aid anum b

Various joins in MySQL 1. Cartesian Product (cross join) In MySQL, you can think of cross join or omit cross as join, or use ',' For example Select * From Table1 cross join Table2 Select * From Table1 join Table2 Select * From Ta

S.sno, Sname, S. Dname, S.cno, MARK, TnameFrom STUDENT as SINNER JOIN TEACHER as TOn S. dnameand S. CNO =t. CNOORDER BY Sname The results of the operation are shown in Figure 9.14. Figure 9.14 Query results with unequal connections Describes that by default, a DBMS executes a multiple-table query by pressing INNER JOIN