![]() See the CASE OPERATOR for details on the CASE operator outside of stored programs. The text on this page describes the CASE statement for stored programs. WHEN search_condition THEN statement_list The resultant table after applying the where clause with left join contains the rows that has amount values greater than 2000. SELECT ID, NAME, DATE, AMOUNT FROM CUSTOMERS Consider the previous two tables CUSTOMERS and ORDERS and join them using the left join query by applying some constraints using the WHERE clause. ![]() Records in the combined database tables can be filtered using the WHERE clause. The syntax of Left Join when used with WHERE clause is given below − Left Join with WHERE ClauseĪlong with the ON clause, a WHERE clause can also be applied on the obtained result-set after Left Join is implemented. If the orders are not made on the specific dates, NULL is returned. The dates on which these orders are made will also be displayed. Khilan and Chaitali made one order each, that are sold by Revathi and Vivek respectively. The EMPLOYEE table consists of the details of employees in an organization and sales made by them.Īs we can see in the table above, the customer Kaushik made three orders, in which two are sold by employee Alekhya and one is sold by Sarika. Now, we can insert values into this empty tables using the INSERT statement as follows − ![]() In addition to these we will create the EMPLOYEE table using the following query − To demonstrate Left Join with multiple tables, let us consider the previously created tables CUSTOMERS and ORDERS. The syntax to join multiple tables using Left Join is given below − If the records are not matched, NULL is returned. Similar to the Inner Join query, Left Join also joins multiple tables where the first table is returned as it is and the remaining tables are matched with the rows in the first table. The other customers in CUSTOMERS table did not make purchases on the specified dates, so the records are returned as NULL. (1, 'Ramesh', 32, 'Ahmedabad', 2000.00 ),Īs we can see in the table above, only Khilan, Kaushik and Chaitali made purchases on the mentioned dates in ORDERS table hence, the records are matched. Now insert values into this table using the INSERT statement as follows − To understand this query better, let us create some tables in an existing database and join them using Left Join or Left Outer Join.Īssume we have created a table named CUSTOMERS, which contains the personal details of customers including their name, age, address and salary, using the following query. Syntaxįollowing is the basic syntax of Left Join in SQL − If the number of rows in first table is less than the number of rows in second table, the rows in second table that do not have any counterparts in the first table will be discarded from the result. If zero (0) records are matched in the consequent tables, the join will still return a row in the result, but with NULL in each column from the right table. Left Join or Left Outer Join in SQL combines two or more tables, where the first table is returned wholly but, only the matching record(s) are retrieved from the consequent tables. Here, the join operation is presumed based on the join-predicate EmpDetails.EmpID = MaritalStatus.EmpID. Full (Outer) Join: Retrieves records from both the tables and fills the unmatched values with NULL.įollowing diagram illustrates various outer joins between two tables namely, EmpDetails and MaritalStatus.Right (Outer) Join: Retrieves all the records from the second table, Matching records from the first table and NULL values in the unmatched rows.Left (Outer) Join: Retrieves all the records from the first table, Matching records from the second table and NULL values in the unmatched rows.There are three types of outer joins, namely − This scenario only occurs if the left table (or the first table) has more records than the right table (or the second table), or vice versa. ![]() NULL values are displayed against these records where the join condition is not met. Outer Join is used to join multiple database tables into a combined result-set, that includes all the records, even if they don't satisfy the join condition. First of all, let us understand what is outer join. Left Join is a type of outer join that retrieves all the records from the first table and matches them to the records in second table. As we discussed in the previous chapters, there are two types of Joins − This relation is defined using a join condition. Joins are used to retrieve records from two or more tables based on a logical relation between them.
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