在SQL语句中使用局部变量时出现问题

Question

我有以下SQL语句：

<script type="text/javascript">
var websocketServerLocation = '{{urls['websockurl']}}'
</script>
<script type="text/javascript" src="/static/common/js/framework7.min.js"></script>
<script type="text/javascript" src="/static/common/js/reconnecting-websocket.min.js"></script>

我想限制列值返回的行。但是当我跑步时： It doesn't work：

Of course the result of the subquery is a small value：

怎么了？

Answer 1

您需要使用子查询：

SELECT * 
FROM (SELECT DNI, puntaje, @row := @row+1 as Puesto
      FROM postulante, (SELECT @row := 0) r
      WHERE idCa = 2 
        AND idPer = 1 
      ORDER BY puntaje DESC) sub
WHERE Puesto <= (SELECT vacantes 
                FROM carrera_abierta 
                WHERE idCa=2 AND idPer=1)
ORDER BY Puesto;