Question

我有多个彼此相关的表，但我有一个表与这些表中的任何一个都没有关系，并希望在（where子句）中使用该表。那我该怎么做呢？

 /*  this is the table i want to use without join (d_checkupnext_alert.chx_days)
  *  notice : chx_days return on value with one row only
  */

SELECT 
  d_checkupinfo.*,
  d_branch.*,
  d_checkup.*,
  d_patient.*,
  d_checkupnext_alert.chx_days
FROM d_checkupinfo
  LEFT JOIN d_patient ON d_checkupinfo.chi_pi_num = d_patient.pi_id
  LEFT JOIN d_branch ON d_checkupinfo.chi_branch_id = d_branch.branch_id
  LEFT JOIN d_checkup ON d_checkupinfo.chi_type_id = d_checkup.checkup_id
   WHERE CURDATE() BETWEEN DATE_SUB(FROM_UNIXTIME(chi_nextdate), INTERVAL chx_days day) AND FROM_UNIXTIME(chi_nextdate)

/ * update * / 我使用此代码，但它有效，但给我错误

 SET @days = (select chx_days from d_checkupnext_alert LIMIT 1);
 SELECT d_checkupinfo.*, d_branch.*, d_checkup.*,
d_patient.* 
FROM d_checkupinfo
  LEFT JOIN d_patient ON d_checkupinfo.chi_pi_num = d_patient.pi_id
  LEFT JOIN d_branch ON d_checkupinfo.chi_branch_id = d_branch.branch_id
  LEFT JOIN d_checkup ON d_checkupinfo.chi_type_id = d_checkup.checkup_id 
WHERE CURDATE() BETWEEN DATE_SUB(FROM_UNIXTIME(chi_nextdate), INTERVAL @days day) AND FROM_UNIXTIME(chi_nextdate)

Answer 1

最好的方法是使用简单的JOIN或“,”，如下所示：

SELECT 
  d_checkupinfo.*,
  d_branch.*,
  d_checkup.*,
  d_patient.*,
  d_checkupnext_alert.chx_days
FROM d_checkupinfo
  LEFT JOIN d_patient ON d_checkupinfo.chi_pi_num = d_patient.pi_id
  LEFT JOIN d_branch ON d_checkupinfo.chi_branch_id = d_branch.branch_id
  LEFT JOIN d_checkup ON d_checkupinfo.chi_type_id = d_checkup.checkup_id
  , d_checkupnext_alert
   WHERE CURDATE() BETWEEN DATE_SUB(FROM_UNIXTIME(chi_nextdate), INTERVAL chx_days day) AND FROM_UNIXTIME(chi_nextdate)

但如果您不想，可以使用系统变量：请参阅"MySQL System Variables"

如何在mysql中使用没有连接的表

1 个答案: