MySQL Functions - MySQL tutorial for beginners

Following are functions which is most command used in mysql

Least: Return Least value amont all

SELECT LEAST(4,3,8,-1,5);

Greatest: Return greatest value amont all

SELECT GREATEST(4,3,8,-1,5);

Interval(): takes a comparison value as its first argument. The remaining arguments should be a set of values in sorted order. INTERVAL() compares the first argument to the others and returns a value to indicate how many of them are less than or equal to it.

SELECT INTERVAL(2,1,2,3,4);

BETWEEN: The BETWEEN operator takes the two endpoint values of the range and returns true if a comparison value lies between them and The comparison is inclusive.

SELECT * FROM `products` WHERE id between 1 and 10

ISNULL(0): return true if value is NULL

select ISNULL(1)

Group By: The MySQL GROUP BY statement is used along with the SQL aggregate functions like SUM to provide means of grouping the result. IN: This is a clause, which can be used along with any MySQL query to specify a condition.

BETWEEN: This is a clause, which can be used along with any MySQL query to specify a condition.

UNION: Use a UNION operation to combine multiple result sets into one.

COUNT:  COUNT aggregate function is used to count the number of rows in a database table.

MAX: The MAX aggregate function allows us to select the highest (maximum) value for a certain column.

MIN: The MIN aggregate function allows us to select the lowest (minimum) value for a certain column.

AVG: The AVG aggregate function selects the average value for certain table column.

SUM: The SUM aggregate function allows selecting the total for a numeric column.

SQRT: This is used to generate a square root of a given number.

RAND: This is used to generate a random number using MySQL command.

CONCAT: This is used to concatenate any string inside any MySQL command.

Switch Case in Mysql

CASE  case_expression
   WHEN when_expression_1 THEN execute_statement1
   WHEN when_expression_2 THEN execute_statement1 
   ELSE execute_statement
END CASE;

Example 1

set @variable='10';
select (case when (@variable = '10') then "Equal to 10" else "Not Equal to 10" end)

Example 2

set @variable=10;
select (case when (@variable <=10) then "Less Than Equal to 10" else "Greater Than 10" end)

Example 3

set @variable=10;
select (case
            when (@variable <10) then "Less Than Equal to 10"
            when (@variable =10) then "Equal to 10"
        else "Greater Than 10" end)

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mysqlsubqueries examples Scalar Subqueries Row Subqueries Column Subqueries Table Subqueries

It is query very similar to Normal queries in databases like
It may return one column
it may return more column
It may return single rows
It may return multiple rows

OR
any of above combination.

SubQuries are those queries which are used within Normal Queries.

For Example

select * from users where user_id =(select user_id from profile where type='user');

Here queries used within bracket is known as sub queris

There are four types of sub-queries.
a. Scalar Subqueries: return single columan of single row

select * from users where user_id =(select user_id from profile where type='user' limit 1);

b. Row Subqueries: Return single row

select u1.* from users As u1 left join (select user_id,country from profile limit 1) as u2 on u2.user_id=u1.user_id and u2.country=u1.country

c. Column Subqueries: Return one column of one or more rows

select * from users where user_id in(select user_id from profile where type='user');

d. Table Subqueries: return one more col of one/more rows

select u1.* from users As u1 left join (select user_id,country from profile) as u2 on u2.user_id=u1.user_id and u2.country=u1.country

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