在视图的子查询中使用视野

Question

I have a view which has a column which is calculated from other columns. For example, in my original table I have the columns A and B from which I calculate the value of column X in my view. I need the value of X in another column I have in the view - Z . But when I put it in the sub-query of my view I get an Unknown column 'X' in 'field list' SQL statement .

The sub-query of the view looks like this:

    (CASE
            WHEN (`users`.`A` REGEXP '^(regexone)') THEN 'ValueA'
            WHEN (`users`.`B` REGEXP '^(regextwo)') THEN 'ValueB'
            ELSE ''
        END) AS `X`,
    (CASE
            WHEN
                (`X` = 'ValueA')
            THEN
                (`users`.`C`*0.95-0.3)
            ELSE ''
    END) AS 'Z'

What's the correct syntax of using a computed view field in the computation of another field?

Answer 1

if you can you user-defined variables use like

SELECT
@x := (CASE
        WHEN (`users`.`A` REGEXP '^(regexone)') THEN 'ValueA'
        WHEN (`users`.`B` REGEXP '^(regextwo)') THEN 'ValueB'
        ELSE ''
    END) AS `X`,
(CASE
        WHEN
            (@x = 'ValueA')
        THEN
            (`users`.`C`*0.95-0.3)
        ELSE ''
END) AS 'Z'