SQL Convert a char to boolean - mysql

Question

I have in my table one row with a char value. When the value is NULL then a false should be outputted. If the value is not NULL then a true should be outputted.
So when I try to set user_group.tUser to 0 or 1 then I'm getting this error:
Invalid column name 'false'.
Invalid column name 'true'.
SELECT COALESCE((SELECT name
FROM v_company
WHERE companyId = userView.companyId), ' ') AS company,
userView.value AS companyUser,
userView.display AS displayedUser,
CASE
WHEN user_group.tUser IS NULL THEN 0
ELSE 1
END AS userIsMemberOfGroup
FROM v_user userView
LEFT OUTER JOIN cr_user_group user_group
ON ( user_group.group = 'Administrators'
AND user_group.tUser = userView.value )
ORDER BY company ASC,
displayedUser ASC

Answer 1

I think this is the logic you want:
SELECT COALESCE(v.name, ' ') as company,
u.value as companyUser, u.display as displayedUser,
(EXISTS (SELECT 1
FROM cr_user_group ug
WHERE ug.group = 'Administrators' AND
ug.tUser = uv.value
)
) as userIsMemberOfGroup
FROM v_user u LEFT JOIN
v_company c
ON c.companyId = v.companyId
ORDER BY company ASC, displayedUser ASC ;
In general, MySQL is very flexible about going between booleans and numbers, with 0 for false and 1 for true.

Answer 2

You can use MySQL IF function to return 'false' when name IS NULL, else 'true':
SELECT IF(name IS NULL, 'false', 'true')
FROM table;

Answer 3

A simple CASE expression would work here:
SELECT
name,
CASE WHEN name IS NOT NULL THEN true ELSE false END AS name_out
FROM yourTable;
We could also shorten the above a bit using IF:
IF(name IS NOT NULL, true, false)

Answer 4

SELECT
CASE
WHEN name IS NULL THEN 'false'
ELSE 'true'
END
FROM
table1;