A Brief Analysis of the Differences between “:=” and “=” in MySQL

=

Only when setting and updating does it have the same effect as :=, that is, assignment; otherwise it has the effect of equality. In view of this, when using variables to implement line numbers, you must use :=.

:=

It not only has the function of assigning values ​​when setting and updating, but also when selecting.

The following is a comparison of the effects of = and = in select

sql

set @num = 0;
SELECT @num := @num+1 AS rowno, nc as nickname from table_user;

result

sql

set @num = 0;
SELECT @num = @num+1 AS rowno, nc as nickname from table_user;

result

sql

set @num = 0;
SELECT @num = @num AS rowno, nc as nickname from table_user;

result

Reference: https://www.jb51.net/article/167218.htm

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