What is the difference between left join with where clause & LEFT JOIN without where clause?

Asked By: Reza Cize | Last Updated: 19th January, 2020
Category: technology and computing databases
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Case 2: Left Outer join without On and Where Clause
When you use a Left Outer join without an On or Where clause, there is no difference between the On and Where clause. Both produce the same result as in the following.

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Also question is, what is the difference between left join with where clause and left join without where clause?

When you use a Left Outer join without an On or Where clause, there is no difference between the On and Where clause. Both produce the same result as in the following. First we see the result of the left join using neither an On nor a Where clause.

Secondly, can we use where clause with left join? The LEFT JOIN allows you to query data from two or more tables. Similar to the INNER JOIN clause, the LEFT JOIN is an optional clause of the SELECT statement, which appears immediately after the FROM clause. When you use the LEFT JOIN clause, the concepts of the left table and the right table are introduced.

One may also ask, what is the difference between join and where clause?

Rows of the outer table that do not meet the condition specified in the On clause in the join are extended with null values for subordinate columns (columns of the subordinate table), whereas the Where clause filters the rows that actually were returned to the final output.

What happens when you join two tables together without an on clause?

Any JOIN without an ON clause is a CROSS JOIN. The LEFT JOIN is an outer join, which produces a result set with all rows from the table on the "left" (t1); the values for the columns in the other table (t2) depend on whether or not a match was found. JOINs can be concatenated to read results from three or more tables.

35 Related Question Answers Found

Can we use where clause in inner join?

To use the WHERE clause to perform the same join as you perform using the INNER JOIN syntax, enter both the join condition and the additional selection condition in the WHERE clause. The tables to be joined are listed in the FROM clause, separated by commas. This query returns the same output as the previous example.

What is join SQL query?

SQL JOIN
  • A SQL JOIN combines records from two tables.
  • A JOIN locates related column values in the two tables.
  • A query can contain zero, one, or multiple JOIN operations.
  • INNER JOIN is the same as JOIN; the keyword INNER is optional.

Which is better inner join vs where clause?

INNER JOIN is ANSI syntax which you should use. It is generally considered more readable, especially when you join lots of tables. It can also be easily replaced with an OUTER JOIN whenever a need arises. The WHERE syntax is more relational model oriented.

Is join more efficient than where?

3 Answers. For modern RDBMS there is no difference between "explicit JOIN" and "JOIN-in-the-WHERE" (if all JOINS are INNER) regards performance and query plan. Now, the JOIN-before-WHERE is logical processing not actual processing and the modern optimisers are clever enough to realise this.

What is the difference between left join and left outer join?


In SQL, the left join returns all the records from first table and matched records from second table. If there is no match from second table then only records from first table are returned. Basically there is no difference in left join and left outer join. Left outer join also returns same results as left join.

Where clause in left outer join SQL?

About LEFT OUTER Join Operations. The result set of a LEFT OUTER join contains all rows from both tables that meet the WHERE clause criteria, same as an INNER join result set. In addition, any rows from the left table that do not have a matching row that exists in the right table will also be included in the result set

How many tables may be included with a join?

How many tables may be included with a join? Explanation: Join can be used for more than one table. For 'n' tables the no of join conditions required are 'n-1'.

How do you convert left join to inner join?

A LEFT or RIGHT OUTER JOIN is converted to an INNER JOIN if one of the following conditions is true:
  1. a null-intolerant predicate referencing columns of the null-supplying tables is present in the query WHERE clause.
  2. the null-supplying side of an OUTER JOIN returns exactly one row for each row from the preserved side.

What is the meaning of Join In?

(join in something) to do an activity with people who are already doing it.

What is on clause in SQL?


SQL | ON Clause. To specify arbitrary conditions or specify columns to join, the ON Clause is used. The join condition is separated from other search conditions. The ON Clause makes code easy to understand. ON Clause can be used to join columns that have different names.

What are the different type of joins in SQL?

There are four basic types of SQL joins: inner, left, right, and full.

Where vs vs LEFT JOIN?

It takes all rows from the first table, regardless of whether the on clause evaluates to true, false, or NULL . So, filters on the first table have no impact in a left join . Filters on the first table should be in the where clause. Filters on the second table should be in the on clause.

What is the difference between and condition and/or condition?

As nouns the difference between condition and conditions
is that condition is a logical clause or phrase that a conditional statement uses the phrase can either be true or false while conditions is .

Which table is left in left join?

The left table is the table that is in the FROM clause, or left of the join condition, the join clause here. And a right table is on the right side of the join clause. When we speak of a left outer join, what we're saying is, take all the rows from the left table, and join them to rows on the right table.

Where LEFT JOIN is null?


The SQL LEFT JOIN returns all rows from the left table, even if there are no matches in the right table. This means that if the ON clause matches 0 (zero) records in the right table; the join will still return a row in the result, but with NULL in each column from the right table.

IS NULL in SQL?

The IS NULL condition is used in SQL to test for a NULL value. It returns TRUE if a NULL value is found, otherwise it returns FALSE. It can be used in a SELECT, INSERT, UPDATE, or DELETE statement.

How does LEFT JOIN work?

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. In short, the LEFT JOIN clause returns all rows from the left table (T1) and matching rows or NULL values from the right table (T2).