Can you have a subquery in a view?
Subqueries cannot be used in the FROM clause of a view. There is a general principle that you cannot modify a table and select from the same table in a subquery.
Why do we use subqueries in SQL?
A Subquery or Inner query or a Nested query is a query within another SQL query and embedded within the WHERE clause. A subquery is used to return data that will be used in the main query as a condition to further restrict the data to be retrieved. A subquery cannot be immediately enclosed in a set function.
When to use a subquery in SQL query?
SQL – Sub Queries. A subquery is used to return data that will be used in the main query as a condition to further restrict the data to be retrieved. Subqueries can be used with the SELECT, INSERT, UPDATE, and DELETE statements along with the operators like =, <, >, >=, <=, IN, BETWEEN, etc.
How to create view with subquery in MySQL?
CREATE VIEW v_max_year AS SELECT alias, MAX (year) as max_year FROM a GROUP BY a.alias; CREATE VIEW v_latest_info AS SELECT a.* FROM a JOIN v_max_year b ON a.alias=b.alias and a.year=b.max_year; It works fine on mysql 5.0.45, without much of a speed penalty (compared to executing the original sub-query select without any views).
Is it possible to run sub query SELECT without views?
It works fine on mysql 5.0.45, without much of a speed penalty (compared to executing the original sub-query select without any views). It appears to be a known issue.
Can a subquery have more than one column?
There are a few rules that subqueries must follow − Subqueries must be enclosed within parentheses. A subquery can have only one column in the SELECT clause, unless multiple columns are in the main query for the subquery to compare its selected columns. An ORDER BY command cannot be used in a subquery, although the main query can use an ORDER BY.