What is left and right outer join in SQL?

The key difference between a left outer join, and a right outer join is that in a left outer join it’s the table in the FROM clause whose all rows are returned. Whereas, in a right outer join we are returning all rows from the table specified in the join clause.

What is left and right outer join?

There are two kinds of OUTER joins in SQL, LEFT OUTER join and RIGHT OUTER join. … LEFT outer join includes unmatched rows from the table written on the left of the join predicate. On the other hand, RIGHT OUTER join, along with all matching rows, includes unmatched rows from the right side of the table.

What is a left outer join in SQL?

SQL left outer join is also known as SQL left join. … SQL left outer join returns all rows in the left table (A) and all the matching rows found in the right table (B). It means the result of the SQL left join always contains the rows in the left table.

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What is difference between left and right join in SQL?

The LEFT JOIN includes all records from the left side and matched rows from the right table, whereas RIGHT JOIN returns all rows from the right side and unmatched rows from the left table. …

What is the difference between left and left outer join?

There really is no difference between a LEFT JOIN and a LEFT OUTER JOIN. Both versions of the syntax will produce the exact same result in PL/SQL. Some people do recommend including outer in a LEFT JOIN clause so it’s clear that you’re creating an outer join, but that’s entirely optional.

Are left and right joins interchangeable?

9 Answers. are indeed completely interchangeable. Try however Table2 left join Table1 (or its identical pair, Table1 right join Table2 ) to see a difference. This query should give you more rows, since Table2 contains a row with an id which is not present in Table1.

Why right outer join is needed?

The only reason I can think of to use RIGHT OUTER JOIN is to try to make your SQL more self-documenting. You might possibly want to use left joins for queries that have null rows in the dependent (many) side of one-to-many relationships and right joins on those queries that generate null rows in the independent side.

Is outer join and full join same?

The Outer Join includes the matching rows as well as some of the non-matching rows between the two tables. An Outer join basically differs from the Inner join in how it handles the false match condition. … Full Outer Join: It combines the result of the Left Outer Join and Right Outer Join.

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What is equi join?

An equi join is a type of join that combines tables based on matching values in specified columns. … The column names do not need to be the same. The resultant table contains repeated columns. It is possible to perform an equi join on more than two tables.

What is the function of a full outer join?

What is the function of a full outer join? Explanation: The full outer join operation preserves the tuples named on both the sides of the operation. Unlike the inner join, outer joins preserve tuples from either or both sides of the operation. 6.

IS LEFT join faster than inner join?

A LEFT JOIN is absolutely not faster than an INNER JOIN . In fact, it’s slower; by definition, an outer join ( LEFT JOIN or RIGHT JOIN ) has to do all the work of an INNER JOIN plus the extra work of null-extending the results.

Which join is best in SQL?

There is not a “better” or a “worse” join type. They have different meaning and they must be used depending on it. In your case, you probably do not have employees with no work_log (no rows in that table), so LEFT JOIN and JOIN will be equivalent in results.

Why LEFT join is used in SQL?

The LEFT JOIN clause allows you to query data from multiple tables. It returns all rows from the left table and the matching rows from the right table. If no matching rows found in the right table, NULL are used. … For each row from the T1 table, the query compares it with all the rows from the T2 table.

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