SQL SELECT
SQL SELECT statement is used to select or get data from a database, as a result set.
Syntax
The syntax of a SQL SELECT statement is
SELECT select_list [ INTO new_table ]
[ FROM table_source ] [ WHERE search_condition ]
[ GROUP BY group_by_expression ]
[ HAVING search_condition ]
[ ORDER BY order_expression [ ASC | DESC ] ]
Select All Columns from Table
SQL SELECT Query to select all columns from table table_source
is
SELECT *
FROM table_source;
Examples
SELECT * FROM students;
SELECT * FROM employees;
Select Single Column from Table
SQL SELECT Query to select a specific column column1
from table table_source
is
SELECT column1
FROM table_source;
Examples
SELECT name FROM students;
SELECT salary FROM employees;
Select Multiple Columns from Table
SQL SELECT Query to select multiple columns column1
, column2
, and column3
from table table_source
is
SELECT column1, column2, column3
FROM table_source;
Examples
SELECT name, rollno FROM students;
SELECT name, id, role FROM employees;
Select from Table based on a Condition
SQL SELECT Query to select rows from table table_source
based on a condition is
SELECT *
FROM table_source
WHERE condition;
Examples
SELECT * FROM students WHERE name='Arjun';
SELECT * FROM students WHERE rollno > 12;
SELECT * FROM employees WHERE id=25;
SELECT * FROM employees WHERE name LIKE '%John%';
Select from Table and Group By Column(s)
SQL SELECT Query to select rows from table table_source
and group them by column column1
is
SELECT *
FROM table_source
GROUP BY column1;
Examples
SELECT * FROM students GROUP BY locality;
SELECT * FROM employees GROUP BY role;
Select from Table and Group By Column(s), Having Search Condition
SQL SELECT Query to select rows from table table_source
, group them by column column1
and then having to pass the search condition SUM(column2) > 1000
.
SELECT column1, SUM(column2) AS column2_sum
FROM table_source
GROUP BY column1
HAVING SUM(column2) > 1000;
HAVING clause can be only used with GROUP BY clause.
Examples
SELECT role, SUM(salary) FROM employees GROUP BY role HAVING SUM(salary) > 2000.0;
Select from Table and Order By Column(s)
SQL SELECT Query to select rows from table table_source
and order them by column column1
is
SELECT *
FROM table_source
ORDER BY column1;
Ascending is the default order. To order the rows in descending order of specific column, say column1
, then the SQL SELECT Query is
SELECT *
FROM table_source
ORDER BY column1 DESC;
Examples
SELECT * FROM students ORDER BY name;
SELECT * FROM students ORDER BY name ASC;
SELECT * FROM students ORDER BY name DESC;
SELECT * FROM students ORDER BY name, locality;