Label:1, Cross join: There are two, explicit and implicit, without an ON clause, returns the product of two tables, also known as the Cartesian product, the number of returned records should be in a and B table in accordance with the record and. Explicit: SELECT [Cols_list] from aCross Joinb where [condition] implicit: SELECT [Cols_list] from a,b where [condition] 2, INNER join (INNER
Tags: Connection Method field name comparison field record right outer connection outer JOIN mode use 1-- inner connection: INNER JOIN It represents a matching record that returns two tables or Recordset join fields, representing the portions
of the two tables that are cont
: FULL OUTER JOIN ).Select o. ID, O. ORDER_NUMBER, O. CUSTOMER_ID, C. ID, C. NAMEFrom orders o full outer join MERs c on c. ID = O. CUSTOMER_ID;Note: MySQL does not support all external connections. The method provided here is suitable for Oracle and DB2. However, you can ob
follow the join condition after ON, and write the conditions for the central table to the WHERE clause.Statement 9: FULL OUTER JOIN ).Select o. ID, O. ORDER_NUMBER, O. CUSTOMER_ID, C. ID, C. NAMEFrom orders o full outer join mers c on c. ID = O. CUSTOMER_ID;Note: MySQL does
table to the WHERE clause.
Statement 9: Full outer join ).Select O. ID, O. order_number, O. customer_id, C. ID, C. NameFrom orders o full outer join MERs C on C. ID = O. customer_id;Note: MySQL does not support all external connections. The method provided here is suitable for Oracle and
SQL left Outer Join, right Outer Join, full join, internal joinThe connection conditions can be specified in the from or where clause. We recommend that you specify the connection conditions in the from clause. The where and having clauses can also contain search conditions
The connection conditions can be specified in the FROM or WHERE clause. We recommend that you specify the connection conditions in the FROM clause. The WHERE and HAVING clauses can also contain search conditions to further filter the rows selected by the connection conditions.Connections can be divided into the following types:Internal Connection.(Typical join operations use comparison operators such as = or Equal connection and natural connection.The
? The connection conditions can be specified in the from or where clause. We recommend that you specify the connection conditions in the from clause. The where and having clauses can also contain search conditions to further filter the rows selected by the connection conditions.
Connections can be divided into the following types:
Internal Connection.(Typical join operations use comparison operators such as = or Equal connection and natural connectio
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 join conditions. Connections can be divided into the followin
This connection is often used in early query statements, which is a small problem. Therefore, I checked the information and summarized it as follows:
External connections are easier to understand,A. It is generally used in some classification codes. For example, if you have an employee information table, the position information isCodeAnd the meaning of this Code is described in the position table.B. Classified information storage. For example, in the preceding employee information table, the
Type DefinitionThe inner connection only connects the matched rows.The left Outer Join contains all rows in the left table (no matter whether the table on the right has rows matching them) and all matched rows in the right tableThe right Outer Join contains all rows in the right table (no matter whether the left table
First, the concept
1. Left join the left outer join
To the left table, go to the right table to find the same field, if more than one will be listed in sequence
2. Connect Join
Find the same records around the same
3. Fully connected full outer
Original link: http://www.powerxing.com/sql-join/In general, the use/difference of four joins can be described as:
The LEFT join returns all records from the table (shop), even if there are no matching rows in the right table (Sale_detail).
Right outer join, returns all records in the right table, even if
1 common table connections (inner join,left join,right join,full Join,cross join)if object_id(N'table1'N'U') is not NULL Drop Tabletable1if object_id(N'table2'N'U') is not NULL Drop Tabletable2Create TableTable1 (IDint, namevarchar( -))Insert intotable1Select 1,'Xia
2016-6-12 22:35:51Working for more than a year of Oracle, recently learning MySQL, think carefully about the various connections, feel these concepts are quite annoying! Recently organized a bit, share their own understanding, some things are borrowed from the Internet and absorbed by themselves.1. No matter what the connection is, the principle of Oracle and MySQL is exactly the same, but some of the wording is different. Speaking of writing, here's a little bit.SELECT * from A, B where a.filed
1. Internal Connection is simpleSelect a. *, B. * from a, B where a. ID = B. IDSelect a. *, B. * from a inner join B on A. ID = B. IDThe above two statements are completely equivalent.
2. left Outer JoinSelect * from EMP a left join dept D on A. deptno = D. deptnoSelect * from emp a, DEPT d Where a. deptno = D. deptno (+)
The above two statements are completely e
tables) horizontally, and produce a new result set by combining rows from one data source with rows that match it into a single new tuple.SQL provides several types of connection methods, the difference being that the method used to select the rows to connect from each overlapping set of data is different.Connection type definitionAn inner join connects only matching rowsThe left OUTER
locate the intersection of two sequences. After the inner join operation, elements from the two sequences that meet the specified conditions will be combined to form a new sequence. The join operator implements inner join based on key matching in the element.
3. left Outer Join
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