SQL LEFT JOINS
SQL JOINS are used to combine records from two or more tables in a database.
To apply a join in both tables, it is necessary to have at least one relative(common) column.
We can combine up to 32 tables in a single query.
Syntax:
SELECT table1.column1 , table2.column2 FROM table1.columnname JOIN table2.columnname ;
Let’s understand the LEFT JOIN with an example. For Demo, we will be using the Emp and Project Tables.
Table Emp
Table Project
To generate a result set through joins, we can utilize both the emp and project tables.
The relative column between the two tables is Ecode.
LEFT OUTER JOIN returns all records from the left table and the matched records from the right table. Null output will be given for records in the left table that have no match in the right table.
LEFT OUTER JOIN Example :
Objective: In this example, we will retrieve all the records from the Emp table(Left Table). If there is a matching Ecode in the Project table(Right Table) and the Emp table, the value will be taken from the Project table else Project table will give NULL value.
SELECT e.Ecode, e.FirstName, e.LastName, p.Project FROM Tbl_Emp as e LEFT JOIN Tbl_Project as p on e.Ecode = P.Ecode;
Output:
