How to declare a variable in MySQL?

Question

How to declare a variable in mysql, so that my second query can use it?

I would like to write something like:

SET start = 1;
SET finish = 10;

SELECT         


        

Answer 1

SET

SET @var_name = value 

OR

SET @var := value

both operators = and := are accepted

---

SELECT

SELECT col1, @var_name := col2 from tb_name WHERE "conditon";

if multiple record sets found only the last value in col2 is keep (override);

SELECT col1, col2 INTO @var_name, col3 FROM .....

in this case the result of select is not containing col2 values

---

Ex both methods used

-- TRIGGER_BEFORE_INSERT --- setting a column value from calculations

...
SELECT count(*) INTO @NR FROM a_table WHERE a_condition;
SET NEW.ord_col =  IFNULL( @NR, 0 ) + 1;
...