La primera declaración en UNION devuelve cuatro columnas:
SELECT b.id AS id,
b.pid AS pid,
b.message AS message,
b.date AS date
FROM wall_posts AS b
El segundo devuelve seis , porque * se expande para incluir todas las columnas de WALL_POSTS
:
SELECT b.id,
b.date,
b.privacy,
b.pid.
b.uid message
FROM wall_posts AS b
La UNION
y UNION ALL
los operadores requieren que:
- Existe el mismo número de columnas en todas las declaraciones que componen la consulta de UNION
- Los tipos de datos deben coincidir en cada posición/columna
Usar:
FROM ((SELECT b.id AS id,
b.pid AS pid,
b.message AS message,
b.date AS date
FROM wall_posts AS b
JOIN Friends AS f ON f.id = b.pid
WHERE f.buddy_id = '1' AND f.status = 'b'
ORDER BY date DESC
LIMIT 0, 10)
UNION
(SELECT id,
pid,
message,
date
FROM wall_posts
WHERE pid = '1'
ORDER BY date DESC
LIMIT 0, 10))