Expert PHP and Mysql

SELECT IFNULL(NULL,’Value is NULL’) AS result1, IFNULL(1 > 2, ‘NULL result’) AS result2;

mysql> SELECT NULLIF(TRUE,TRUE) AS istrue, NULLIF(TRUE,FALSE) AS isfalse, NULLIF(TRUE,NULL) AS isnull;

MySQL has four logic control operators: AND, OR, NOT, and XOR. Three of these operators also have shorthand notations: && (AND), || (OR), ! (NOT). These shorthand notations should not be confused with the Bit operators, which are single characters of & and |.

SELECT IF (2 > 1,’2 is greater than 1’,’2 is not greater than 1’) AS answer;

mysql> SET @value=CONVERT(RAND()* 10, UNSIGNED INTEGER);

mysql> SELECT @value, -> CASE -> WHEN @value < 3 THEN ‘Value is < 3’ -> WHEN @value > 6 THEN ‘Value is > 6’ -> WHEN @value = 3 OR @value = 6 THEN ‘Value is 3 or 6’ -> ELSE ‘Value is 4 or 5’ -> END;

mysql> SELECT IFNULL(NULL,’Value is NULL’) AS result1, IFNULL(1 > 2, ‘NULL result’) AS result2;

mysql> CREATE TABLE example ( -> currency ENUM(‘USD’,’CAD’,’AUD’) NOT NULL -> ) ENGINE=InnoDB DEFAULT CHARSET latin1;

mysql> ALTER TABLE flags -> ADD FOREIGN KEY (color) -> REFERENCES colors (color) -> ON DELETE CASCADE;

mysql> SHOW WARNINGS;

mysql> SET SESSION sql_mode=’TRADITIONAL’;

sql_mode=NO_ENGINE_SUBSTITUTION

SELECT DISTINCT f.color FROM flags f WHERE EXISTS (SELECT 1 FROM colors c WHERE c.color = f.color);

SELECT DISTINCT f.country, (SELECT GROUP_CONCAT(color) FROM flags f2 WHERE f2.country = f.country) AS colors FROM flags f;