What is the difference between left join with where clause & left join with no where clause?

Asked By: Silvano | Last Updated: 4th June, 2020
Category: technology and computing databases
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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.

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Likewise, people ask, what is the difference between left join with where clause & left join with no 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.

Also Know, 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.

Also know, 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.

Where condition in joins in SQL?

The WHERE clause filters the result of the FROM clause along with the JOINs while the ON clause is used to produce the table result between the FROM and the JOIN tables. If you want to produce a table result that joins two tables, then you should the ON clause to determine how the tables are joined.

34 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.

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.

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.

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.

Are joins faster than where clauses?


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.

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 where clause in SQL?

A WHERE clause in SQL specifies that a SQL Data Manipulation Language (DML) statement should only affect rows that meet specified criteria. In brief SQL WHERE clause is used to extract only those results from a SQL statement, such as: SELECT, INSERT, UPDATE, or DELETE statement.

Where vs vs SQL?


The difference between the having and where clause in SQL is that the where clause cannot be used with aggregates, but the having clause can. The where clause works on row's data, not on aggregated data.

What are the different type of joins in SQL?

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

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.

Can LEFT JOIN increase row count?


Left joins can increase the number of rows in the left table if there are multiple matches in the right table. Ideally, you'd be able to handle multiple matches on the join inside of the EG Join Tables layout directly.

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.

Does LEFT JOIN return duplicate rows?

Join duplications
For example, if you have a left table with 10 rows, you are guaranteed to have at least 10 rows after the join, but you may also have 20 or 100 depending on what you are joining to. This happens twice, once for each "Tissues" row in the left table, yielding two duplicated rows.