sql join with where clause example

I. Concepts 1. Cross join)Without the WHERE clause, it returns the Cartesian product of the two joined tables, and the number of rows returned is equal to the product of the number of rows in the two tables.For example:A: select a. *, B. * From Table1 A, Table2 B where a. ID = B. IDB: Select * From Table1 a cross join Table2 B where a. ID = B. IDIt is generally n

Left join returns records that include all records in the left table and join fields in the right table.Right join returns records that include all records in the right table and the joined fields in the left table.Inner join (equivalent join) returns only rows with equal

, you can use keyword join to get data from two tables If you want to list everyone's subscriptions, you can use the following SELECT statement SELECT Persons.lastname, Persons.firstname, Orders.orderno from Persons INNER JOIN Orders on persons.id_p = Orders.id_p ORDER by Persons.lastname Result set: LastName FirstName OrderNo Adams John 22456

Http://www.blogjava.net/zolly/archive/2007/10/23/SQLJION.html The join condition can be specified in the from or where clause. We recommend that you specify the join condition in the from clause. The where and having clauses can also contain search conditions to further filter the rows selected by the

Label:--Build Table Table1,table2:CREATE TABLE table1 (ID int,name varchar (10))CREATE TABLE table2 (ID int,score int)Insert INTO table1 Select 1,leeInsert INTO table1 Select 2,zhangInsert INTO table1 Select 4,wangInsert INTO table2 Select 1,90Insert INTO table2 Select 2,100Insert INTO table2 select 3,70such as table-------------------------------------------------Table1 | table2 |-------------------------------------------------ID Name |id Score |1 Lee | 90 |2 Zhang 100 |4 Wang |3 70 |---------

compared, they must have consistent data types.The from clause of the SELECT statement can specify the following types of connections:Result set corresponding to the from clause keywordCross join Cartesian Product (all possible row pairs)Inner join only applies to columns in cross that meet the connection conditions.L

statement, which in this case refers to Categories.CategoryID. You can also link multiple on clauses in a JOIN statement, using the following syntax: SELECT fieldsFrom table1 INNER JOIN table2On table1.field1 compopr table2.field1 andOn table1.field2 compopr table2.field2 OROn table1.field3 compopr table2.field3; You can also nest JOIN statements with the follow

Note: In relational databases, join can be used for operations on multiple tables.Inner join, outer join, and cross join. Similarly, in the LINQ query syntax, join clauses are also very important in Multi-Table operations,UseJoinClauses can be used to associate elements from

5 a20050115 Table B records such as the following:BID bname1 20060324012 20060324023 20060324034 20060324048 2006032408 Experiments such as the following:1.left Join SQL statements such as the following:SELECT * FROM ALeft JOIN BOn a.aid = B.bid The results are as follows:AID Anum BID bname1 a20050111 1 20060324012 a20050112 2 20060324023 a20050113 3 20060324

21. C # sequence consideration, sorting, let clause, and join (Chapter 11, 11.3-11.5 ), Haha, after a week, I have to publish an article about how to read more books ~~~ Use the where clause for consideration The syntax format of the where clause is as follows: where excessive expressions

Categories.CategoryID.You can also link multiple on clauses in a JOIN statement, using the following syntax:SELECT fieldsFrom table1 INNER JOIN table2On table1.field1 compopr table2.field1 andOn table1.field2 compopr table2.field2 OROn table1.field3 compopr table2.field3;You can also nest JOIN statements with the following syntax:SELECT fieldsFrom table1 INNER

Categories.CategoryID.You can also link multiple on clauses in a JOIN statement, using the following syntax:SELECT fieldsFrom table1 INNER JOIN table2On table1.field1 compopr table2.field1 andOn table1.field2 compopr table2.field2 OROn table1.field3 compopr table2.field3;You can also nest JOIN statements with the following syntax:SELECT fieldsFrom table1 INNER

a20050113 3 20060324034 a20050114 4 20060324045 a20050115 NULL NULL(The number of rows affected is 5 rows)Result Description :The left join is based on the records of Table A, a can be regarded as the right table, and B can be regarded as left table.In other words, the records of the left table (A) will all be represented, and the right table (B) will only display records that match the search criteria (in the ex