mongodb inner join

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, na

Tags: suggest a code empty ONS ... select null tarIn 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 no record matches it in the left table Full outer

In-depth understanding of four SQL connections-left outer join, right outer join, inner join, and full link bitsCN.com 1. INNER JOIN(Typical join operations use comparison operators suc

1. Inner join(Typical join operations use comparison operators such as = or The inner join uses the comparison operator to match rows in two tables based on the values of the columns in each table. For example, retrieve all rows with the same student ID in the students and c

1. Inner join(Typical join operations use comparison operators such as = or The inner join uses the comparison operator to match rows in two tables based on the values of the columns in each table. For example, retrieve all rows with the same student ID in the students and c

Adate1 A12 A23 A3Table BBid Bdate1 B12 B24 B4Two tables A, B connected, to remove fields with the same IDSELECT * from a INNER join B on a.aid = B.bid This is only the matching data is taken out.At this point, the removal is:1 A1 B12 A2 B2Then the left join means:SELECT * from a LEFT join B on a.aid = B.bidFirst remov

null. :mysql> SELECT g.goods_name,g.cat_id as g_cat_id, c.cat_id as c_cat_id,c.cat_id from Mingoods G left JOIN mincategory C on g.cat_id = c.cat_id; 　　 3. Right join query ... on ...Syntax: Select A.field1,a.field2,..., b.field3,b.field4 from join on The right connection query is similar to the left JOIN query,

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 not recommended to use methods A and B, becaus

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

list column for the other table contains a null value. If there are matching rows between the tables, the entire result set row contains the data values of the base table.(2) SQL statementsSELECT * FROM table1 full join table2 on Table1.id=table2.id-------------Results-------------ID Name ID Score------------------------------1 Lee 1 902 Zhang 2 1004 Wang Null NULLNULL NULL 3 70------------------------------Note: Returns the left and right connected

9.3.3 INNER JOIN (INNER join) The inner join is also called an equivalent connection, and the result set returned is all the matching data in the two tables, and the mismatched data is discarded. That is, in such a query, the DBMS

Label:Test Table SQL statementCreate TableA (IDintUnsigned not NULL Primary Keyauto_increment, nameChar( -) not NULL default "') Engine=MyISAMdefaultCharSet=UTF8;Create TableB (IDintUnsigned not NULL Primary Keyauto_increment, nameChar( -) not NULL default "', a_idint not NULL) Engine=MyISAMdefaultCharSet=UTF8;Insert intoAValues(NULL,'Zhang San'),(NULL,'John Doe'),(NULL,'Harry');Insert intoBValues(NULL,'Tom',1),(NULL,'Jack',2),(NULL,'Wally',1),(NULL,'Joan',4);Table results:Table A. Table BINN

Inner join There are two tables A and B. The structure of Table A is as follows: Aid: int; identifies the seed, primary key, and auto-increment ID Aname: varchar The data, that is, the records from select * From A, are shown in 1: Figure 1: data in Table Table B has the following structure: Bid: int; identifies the seed, primary key, and auto-increment ID Bnameid: int Data, that

all expressed, while the right table (B) only displays records that meet the search criteria (in this example:. aid = B. bid ).All records in Table B are null.--------------------------------------------2. Right joinThe SQL statement is as follows: select * from A right join B on A.aID = B.bID The result is as follows:Aid anum bid bname1 a20050111 1 20060324012 a20050112 2 20060324023 a20050113 3 20060324034 a20050114 4 2006032404Null null 8 20060324

join column. If a row in the left table does not match a row in the right table, all selection list columns in the right table in the row of the associated result set are null.Right join or right outer join.The right outer connection is the reverse connection of the left outer connection. All rows in the right table are returned. If a row in the right table does not match a row in the left table, a null va

Label:Transferred from: http://blog.csdn.net/jz20110918/article/details/41806611 Let's say we have two tables. Table A is the sheet on the left. Table B is the list on the right. Each of them has four records, of which two records name is the same, as follows: Let's look at the different joins Table A Id Name 1 Pirate 2 Monkey 3 Ninja 4 Spaghetti

2006032402 3 a20050113 3 2006032403 4 a20050114 4 2006032404 Null null 8 2006032408 (The number of affected rows is 5) Result description: After careful observation, we will find that the result of left join is exactly the opposite. This time, it is based on the right table (B) and is filled with null when table A is insufficient. 3. Inner join The SQL stateme

Let's start by looking at the results of the left join and the right join and the Inner join and the full join working on the table. Create a new two table in the database and insert the data you want to test. New table:[SQL]View PlainCopyUse [Test]GO/****** ob

Tags: http strong ar Data div sp on ad efLet's start by looking at the results of the left join and the right join and the Inner join and the full join working on the table. Create a new two table in the database and insert the data you want to test. New table:[SQL]Use

Reprinted from: http://www.cnblogs.com/still-windows7/archive/2012/10/22/2734613.htmlPrerequisites: Suppose there are two tables, one is the student table and the other is the Student score table.The table data are:One, internal connection-inner jion:The most common connection query may be that of identifying the student's name and score:Select S.name,m.mark from student S,mark m where S.id=m.studentidThe above is our most common