如何使用MySql从查询输出中排除记录（基于某些特定条件）？

我不太喜欢SQL，我有以下问题：如果验证了特定条件，我必须从查询输出中排除特定记录

我的查询可以返回0、1、>1条记录：

SELECT
    LS.id                                                                                                       AS livestock_id,
    LS.parent_livestock_species_id                                                                              AS parent_livestock_species_id,
    LS.livestock_species_name_en                                                                                AS livestock_species_name_en,
    IFNULL(LSN.livestock_species_name, LS.livestock_species_name_en)                                            AS livestock_species_name,        
    LSN.description                                                                                             AS description,
    LS.image_link                                                                                               AS image_link,
    (
        select count(*) from LivestockSpecies ls2 where ls2.id = 1 or ls2.parent_livestock_species_id = 1
    ) as total_number
FROM LivestockSpecies                                                                                          AS LS
LEFT JOIN LivestockSpeciesName                                                                                 AS LSN
      ON LSN.livestock_species_id = LS.id AND LSN.language_id = 1
WHERE
    LS.id = 1
OR
    LS.parent_livestock_species_id = 1

total_number字段统计返回的记录总数，并显示在每一行中

我想知道，如果这个总数字段包含一个大于1的值，并且如果父项牲畜物种id字段值为**null*则从查询输出中排除该记录

---

我可以使用SQL执行类似操作吗？

在MySQL中，可以添加一个

having

子句：

having total_number = 1 or parent_livestock_species_id is not null

---

这回答了你的具体问题。可能有更合适的方法来完成你真正想完成的事情。

添加一个

HAVING

子句

SELECT
          LS.id                                                            AS livestock_id
        , LS.parent_livestock_species_id                                   AS parent_livestock_species_id
        , LS.livestock_species_name_en                                     AS livestock_species_name_en
        , IsNULL(LSN.livestock_species_name, LS.livestock_species_name_en) AS livestock_species_name
        , LSN.description                                                  AS description
        , LS.image_link                                                    AS image_link
        , (
                 select
                        count(*)
                 from
                        LivestockSpecies ls2
                 where
                        ls2.id                             = 1
                        or ls2.parent_livestock_species_id = 1
          )
          as total_number
FROM
          LivestockSpecies AS LS
          LEFT JOIN
                    LivestockSpeciesName AS LSN
                    ON
                              LSN.livestock_species_id = LS.id
                              AND LSN.language_id      = 1
WHERE
          LS.id                             = 1
          OR LS.parent_livestock_species_id = 1

GROUP BY
          LS.id
        , LS.parent_livestock_species_id
        , LS.livestock_species_name_en
        , IsNULL(LSN.livestock_species_name, LS.livestock_species_name_en)
        , LSN.description
        , LS.image_link

HAVING
          (
                 select
                        count(*)
                 from
                        LivestockSpecies ls2
                 where
                        ls2.id                             = 1
                        or ls2.parent_livestock_species_id = 1
          )
          > 1

---

查询中使用的表别名从未定义。@jarlh您是什么意思？从LivestockSpecies LS…@jarlh他们是，您只需向右滚动即可，因为格式很糟糕：D@B3S，我很高兴你找到了它们！

SELECT
    LS.id AS livestock_id,
    LS.parent_livestock_species_id AS parent_livestock_species_id,
    LS.livestock_species_name_en AS livestock_species_name_en,
    IFNULL(LSN.livestock_species_name, LS.livestock_species_name_en) AS livestock_species_name,        
    LSN.description AS description,
    LS.image_link AS image_link,
    ls2.total_number as total_number
FROM LivestockSpecies AS LS
INNER JOIN (
   SELECT count(*) AS total_number 
   FROM LivestockSpecies ls2 
   WHERE ls2.id = 1 OR ls2.parent_livestock_species_id = 1
    ) ls2
  ON 1=1 AND ls2.total_number>0
LEFT JOIN LivestockSpeciesName AS LSN
      ON LSN.livestock_species_id = LS.id AND LSN.language_id = 1
WHERE
    LS.id = 1