SQL - Sub Queries
SQL - Sub Queries
A Subquery or Inner query or 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.
Subqueries can be used with the SELECT, INSERT, UPDATE, and DELETE statements along with the operators like =, <, >, >=, <=, IN, BETWEEN etc.
Example
SELECT sub.*
FROM (
SELECT *
FROM tutorial.sf_crime_incidents_2014_01
WHERE day_of_week = 'Friday'
) sub
WHERE sub.resolution = 'NONE'
First, the database runs the “inner query” — the part between the parentheses:
SELECT *
FROM tutorial.sf_crime_incidents_2014_01
WHERE day_of_week = 'Friday'
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