sql join 2 tables

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 JOIN (equivalent join) returns only rows that have the same

first, data constructionFirst build the table, then talk.Create DatabaseTest UseTestCreate TableA (AIDint Identity(1,1)Primary Key, namenvarchar( -), ageint)Create TableB (BIDint Identity(1,1)Primary Key, namenvarchar( -), Genderint)After creation, insert dataInsertA (Name,age)Values('Zhang San', *)InsertA (Name,age)Values('John Doe', -)InsertA (Name,age)Values('XXX', *)InsertA (Name,age)Values('YYY', *)InsertB (Name,gender)Values('Zhang San',1)InsertB (Name,gender)Values('John Doe',1)InsertB (N

SQL inline syntax basic syntax (innerjoin) SELECT * FROM Table 1innerjoin table 2on table 1. userid table 2. useridsql inline syntax description: The preceding statement is used to query two tables, table 1 and table 2. If the userid fields in the two tables are the same, a

To create a database:1 CREATE DATABASETest--The name of the database to be created2 on PRIMARY3 (4 --specific description of the database file5NAME='Test_data',--logical name of the master data file6FILENAME='E:\project\Test_data.mdf',--physical name of the master data file7SIZE=5MB,--Initial size of master data file8MAXSIZE=100MB,--maximum growth of the master data file9FileGrowth= the% --growth rate of master data filesTen ) One LOG on A ( - --the specific

' Teacher ' (' Tid ' int (one) not NULL auto_increment,' Name ' varchar (DEFAULT NULL),' job_title ' varchar DEFAULT NULL,' Major ' varchar DEFAULT NULL,PRIMARY KEY (' tid ')) Engine=innodb auto_increment=6 DEFAULT Charset=utf8; Tutor Table Data Insert INTO ' teacher ' (' tid ', ' name ', ' Job_title ', ' major ') values (1, ' Shen ', ' Professor ', ' image '), (2, ' Liu ', ' Professor ', ' database '), (3, ' Yellow ', ' associate Pro

as follows: AID anum BID bname1 a20050111 1 20060324012 a20050112 2 20060324023 a20050113 3 20060324034 a20050114 4 2006032404The results show: Obviously, this shows only the A.aid=B.bid Records. This shows that inner join is not based on who, it only shows records that match the criteria.--------------------------------------------Note: The LEFT JOIN operation

Tags: load http Select detail LAN margin src lin bleExcerpt from: http://blog.csdn.net/scythe666/article/details/51881235 By default, the inner join, the left join and the right join used in development belong to the outer join, and the outer join also includes the full

thirdtable s on s.col1 = F.col1 G O We get the result is 5 2, why the use of the inner join means that the equivalent condition is not to return a 2, in fact, we can summarize as follows: Conclusion: The reason for using an inner join to return more data than the actual table is that the result set returned by

An introduction to the differences between inner join, outer join, and Cross join in SQL:There are two tables, table A is the one on the left. Table B is the list on the right. Each of them has four records, of which two records have the same name:The result of the 1.INNER JOIN