MySQL去除查询结果重复
发布时间:2020-12-14 18:05:43 所属栏目:大数据 来源:网络整理
导读:出现结果重复数SQL(四表关联): SELECTCOUNT(post.ID )FROM wp_posts AS post LEFT JOINwp_term_relationships AS relationON(post.menu_order =relation.term_order) LEFT JOIN wp_term_taxonomyAS taxonomyON(relation.term_taxonomy_id = taxonomy.term_id
出现结果重复数SQL(四表关联): SELECT
COUNT(post.ID )
FROM wp_posts AS post LEFT JOIN
wp_term_relationships AS relation
ON(post.menu_order =
relation.term_order) LEFT JOIN wp_term_taxonomy
AS taxonomy
ON(relation.term_taxonomy_id = taxonomy.term_id) LEFT JOIN
wp_terms AS
term ON(taxonomy.term_id = term.term_id)
正常的结果应该显示490条数据,但是结果显示了224941。 解决这个办法是在对应的COUNT()里面加上DISTINCT DISTINCT这个关键字主要用于过滤掉多余的重复记录只保留一条,但往往只用它来返回不重复记录的条数,而不是用它来返回不重记录的所有值。 注意:它有局限性,比如吧不能对应多个目标字段,只能对应一个目标字段。 解决重复结果书的SQL如下: SELECT
COUNT(DISTINCT post.ID)
FROM wp_posts AS post LEFT JOIN
wp_term_relationships AS relation
ON(post.menu_order =
relation.term_order) LEFT JOIN wp_term_taxonomy
AS taxonomy
ON(relation.term_taxonomy_id = taxonomy.term_id) LEFT JOIN
wp_terms AS
term ON(taxonomy.term_id = term.term_id)
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