MYSQL Left Join返回与第一个字符匹配的所有行

Question

I've got a simple left join in a MYSQL environment.

SELECT *
FROM (`holiday`)
LEFT JOIN `member` ON `member`.`memberId` = `holiday`.`memberId`
ORDER BY `holiday`.`begin_date` ASC 

However instead of returning only exact matches it is returning any records where the member.memberId has the holiday.memberId in the first character.

Results:

holidayId holiday.memberId member.memberId
9         1                1
9         1A65152F         1
10        1                1
10        1A65152F         1

How do I get it to just return the exact matches?

Answer 1

The field holiday.memberId is a STRING, while member.memberId is a INTEGER, so MySQL automatically casts the string to a Number (eg "123ABC" will be converted to 123).

You could try this:

SELECT *
FROM (`holiday`)
LEFT JOIN `member` ON `member`.`memberId` = BINARY `holiday`.`memberId`
ORDER BY `holiday`.`begin_date` ASC

Using BINARY it will force a binary comparison, disabling the automatic cast.

Or you should convert both fields to string.