How outer join and non-equi are join implemented?

 Non-Equi Join 

Non-Equi Join is also a type of INNER Join in which we need to retrieve data from multiple tables. Non-Equi Join matches the column values from different tables based on an inequality based on the operators like <,>,<=,>=,!=, BETWEEN, etc.

Non-Equi Join in SQL is retrieving data using any operator or condition except the equality condition. The value of the column in each row from the source table is compared with the corresponding value of the target table. If the data matches the source and target table, the comparison returns true, and therefore that data is retrieved from the table.

However, we use the Non-Equi joins for the below-mentioned reasons-

• Retrieving data matching in a range of values.
• Checking for duplicate data between tables.
• For calculating totals.

Syntax

> SELECT *  

FROM TableName1, TableName2  

WHERE TableName1.columnName [> |  < |  >= | <= | != | BETWEEN ] table_name2.column;

OUTER JOIN

The SQL OUTER JOIN returns all rows from both the participating tables which satisfy the join condition along with rows that do not satisfy the join condition. The SQL OUTER JOIN operator (+) is used only on one side of the join condition only.

The subtypes of SQL OUTER JOIN

LEFT OUTER JOIN or LEFT JOIN

RIGHT OUTER JOIN or RIGHT JOIN

FULL OUTER JOIN

Syntax:

Select * 

FROM table1, table2 

WHERE conditions [+];