How to write a MySQL if else endif statement?

Question

I'd like a simple example of a MySQL if, else, endif statement.

I want to do something like this (in Java):

SELECT COUNT(*) FROM  `table` WHERE  `userID` =  1

if(count == 0){
  INSERT INTO  `table` (`userID`,`A` ,`B`)VALUES ('1',  '323',  '232')
}
else{
  UPDATE  `table` SET  `A` =  '323', `B` =  '232' WHERE  `userID` =1
}

Answer 1

MySQL has INSERT ON DUPLICATE KEY UPDATE that allows you to update if the value already exist or Insert if not.

First you need to setup a UNIQUE Constraint,

ALTER TABLE myTable ADD CONSTRAINT tb_uq UNIQUE (ID)

that's it if you want ID to be unique. (This is just an example)

INSERT INTO tableName(userID, A, B) 
VALUES (1, 323, 232)
ON DUPLICATE KEY
UPDATE  A = 323,
        B = 232

• INSERT ... ON DUPLICATE KEY UPDATE Syntax

Answer 2

The if statement (in a stored block):

IF search_condition THEN statement_list
    [ELSEIF search_condition THEN statement_list] ...
    [ELSE statement_list]
END IF

Or the if function (in-line):

IF(expr1,expr2,expr3)

which works as: IF( condition, what_to_do_if_true, what_to_do_if_false ) The last part being the same as an 'else'. An if-else-if would need to be embedded like:

SELECT IF( id==1, "1", IF( ID==2, "2", "Neither" );

Which would do the same as this in most programming languages:

if( id == 1 ) {
    print "1"
} elsif( id == 2 ) {
    print "2"
} else {
    print "Neither"
}