IF, ISNULL

   IF, ISNULL 

MYSQL에서 IF 와 ISNULL 을 조합하여 유용한 조건문 작성이 가능하다

   IF

Example

Return "YES" if the condition is TRUE, or "NO" if the condition is FALSE:

SELECT IF(500<1000, "YES", "NO");

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Definition and Usage

The IF() function returns a value if a condition is TRUE, or another value if a condition is FALSE.

Syntax

IF(condition, value_if_true, value_if_false)

Example

Return 5 if the condition is TRUE, or 10 if the condition is FALSE:

SELECT IF(500<1000, 5, 10);

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Example

Test whether two strings are the same and return "YES" if they are, or "NO" if not:

SELECT IF(STRCMP("hello","bye") = 0, "YES", "NO");

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Example

Return "MORE" if the condition is TRUE, or "LESS" if the condition is FALSE:

SELECT OrderID, Quantity, IF(Quantity>10, "MORE", "LESS")
FROM OrderDetails;

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https://www.w3schools.com/sql/func_mysql_if.asp

   ISNULL

Example

Test whether an expression is NULL:

SELECT ISNULL(NULL);

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Definition and Usage

The ISNULL() function returns 1 or 0 depending on whether an expression is NULL.

If expression is NULL, this function returns 1. Otherwise, it returns 0.

Syntax

ISNULL(expression)

Parameter Values

Parameter	Description
expression	Required. The value to test

Technical Details

Works in:	From MySQL 4.0

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More Examples

Example

Test whether an expression is NULL:

SELECT ISNULL("");

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Example

Test whether an expression is NULL:

SELECT ISNULL(350);

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Example

Test whether an expression is NULL:

SELECT ISNULL("Hello world!");

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https://www.w3schools.com/sql/func_mysql_isnull.asp

   SQL)

IF( ISNULL(B.domain_id) = 1, 'no', 'yes' ) as active