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T-SQL JOINS

T-SQL combines records from two or more tables. It is used to join the records from two or more tables into the database. JOINs are used to connect the fields from many tables by using the values that are equal to each other.

See the below two tables, (a) CUSTOMERS table are as follows -

ID NAME AGE ADDRESS SALARY
1 Hamilton 23 Australia 34000
2 Warner 34 England 22000
3 Martin 28 China 25000
4 Twinkle 30 Turkey 50000
5 Tinu 32 Nepal 45000
6 Michal 31 Bhutan 20000
7 Harper 20 Bangladesh 15000

(b) Another table ORDERS, is as follows -

OID DATE CUSTOMER_ID AMOUNT
100 2020-10-08 00.00.000 3 15000
101 2020-11-20 00.00.000 2 15600
102 2020-10-08 00.00.000 3 30000
103 2019-05-20 00.00.000 4 20600

Let us join two tables in our SELECT statement like below -

The command produces the given output.

T-SQL JOINS

The join is performed in the WHERE clause. Many operators will used to join tables, Like =, <, >, <>, <=, >=, ! =, LIKE, BETWEEN and NOT.

Types of Joins in MS SQL:

There are many types of joins used in MS SQL Server -

  • INNER JOIN
  • LEFT JOIN
  • RIGHT JOIN
  • FULL JOIN
  • SELF JOIN
  • CARTESIAN JOIN
T-SQL JOINS
S.no Description
INNER JOIN It returns rows when there is a match in the tables.
LEFT JOIN It selects records from the first (left-most) table with matching correct table records.
RIGHT JOIN It selects all the rows from the right table, if there are no any matches found in the left table.
FULL JOIN If there is any match in one of the tables then the rows are joining in full join.
SELF JOIN SELF JOIN is used to join a table, if it has two tables, rename at least one table in the MS SQL SERVER.
CARTESIAN JOIN The Cartesian product sets the record of records many connected table in T-SQL.

Example:

Here are two tables named Color and Size, which we have combined with the help of full join.

T-SQL JOINS




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