inner join vs left join

You'll use INNER JOIN when you want to return only records having pair on both sides, and you'll use LEFT JOIN when you need all records from the “left” table, no matter if they have pair in the “right” table or not.

1. What is the difference between an inner join and a left join?
2. IS LEFT JOIN faster than inner join?
3. Is inner join the same as JOIN?
4. IS LEFT JOIN inner or outer?
5. Which is better joins or subqueries?
6. Which join is faster in SQL?
7. Which join is better in SQL?
8. Are subqueries slower than joins?
9. WHY IS LEFT JOIN slow?
10. Why use inner join instead of where?
11. When inner join is used?
12. Which join is like inner join?

What is the difference between an inner join and a left join?

What is the difference between INNER JOIN and LEFT JOIN. Inner join returns only the matching rows between both the tables, non matching rows are eliminated. Left Join or Left Outer Join returns only the matching rows between both the tables, plus non matching rows from the left table.

IS LEFT JOIN faster than inner join?

2 Answers. The Left join seems to be faster because SQL is forced to do the smaller select first and then join to this smaller set of records. For some reason the optimiser doesn't want to do this naturally. Select the first subset of data into a temporary table (or table variable) then join on it.

Is inner join the same as JOIN?

An SQL INNER JOIN is same as JOIN clause, combining rows from two or more tables. An inner join of A and B gives the result of A intersect B, i.e. the inner part of a Venn diagram intersection. Inner joins use a comparison operator to match rows from two tables based on the values in common columns from each table.

IS LEFT JOIN inner or outer?

LEFT JOIN is same as LEFT OUTER JOIN - (Select records from the first (left-most) table with matching right table records.) RIGHT JOIN is same as RIGHT OUTER JOIN - (Select records from the second (right-most) table with matching left table records.) Inner join: Only show rows, when has it data from both of the tables.

Which is better joins or subqueries?

The advantage of a join includes that it executes faster. The retrieval time of the query using joins almost always will be faster than that of a subquery. By using joins, you can maximize the calculation burden on the database i.e., instead of multiple queries using one join query.

Which join is faster in SQL?

9 Answers. 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 better 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. ... In MySQL CROSS JOIN , INNER JOIN and JOIN are the same.

Are subqueries slower than joins?

A general rule is that joins are faster in most cases (99%). The more data tables have, the subqueries are slower. The less data tables have, the subqueries have equivalent speed as joins.

WHY IS LEFT JOIN slow?

The LEFT JOIN query is slower than the INNER JOIN query because it's doing more work. From the EXPLAIN output, it looks like MySQL is doing nested loop join. ... For the INNER JOIN query, MySQL is using an efficient "ref" (index lookup) operation to locate the matching rows.

Why use inner join instead of where?

INNER JOIN is ANSI syntax that you should use. ... The WHERE syntax is more relational model oriented. A result of two tables JOIN ed is a cartesian product of the tables to which a filter is applied which selects only those rows with joining columns matching. It's easier to see this with the WHERE syntax.

When inner join is used?

Inner Join clause in SQL Server creates a new table (not physical) by combining rows that have matching values in two or more tables. This join is based on a logical relationship (or a common field) between the tables and is used to retrieve data that appears in both tables.

Which join is like inner join?

The most important and frequently used of the joins is the INNER JOIN. They are also referred to as an EQUIJOIN. The INNER JOIN creates a new result table by combining column values of two tables (table1 and table2) based upon the join-predicate.