Question

我有2个表，t1和t2，t1保存别名和分数，而t2保存别名及其真实姓名，我希望构建一个查询以获取分数，真实姓名和别名（示例-所需结果）

t1

alias - scores - tl_alias - tm_alias (column names)

tk - 96 - pp - jj
sp - 94 - pp - jj

t2

name - alias - role  (column names)

tom Koshy - tk - user  
shaun penn - sp - user  
peter pan - pp - tl  
john james - jj - tm

所需结果

user_alias - user_name - scores - tl_alias - tl_name - tm_alias - tm_name (column labels)


tk - tom koshy - 96 - pp - peter pan - jj - john james
sp - shaun penn - 94 - pp - peter pan - jj - john james

当前结果

以下查询为我提供了查询中t2.name的所有实例的tl_name，我认为该查询是正确的，但是我想拥有的是，t2.name的第一个实例应显示user_name，然后下一个实例应显示tl_name，然后显示tm_name

SELECT t1.alias,t2.name,t1.scores,t1.tl_alias,t2.name,t1.tm_alias,t2.name from t1 JOIN t2 on t1.tl_alias = t2.alias

tk - peter pan - 96 - pp - peter pan - jj - peter pan
sp - peter pan - 94 - pp - peter pan - jj - peter pan

以下内容也不起作用

SELECT t1.alias,t2.name,t1.scores,t1.tl_alias,t2.name,t1.tm_alias,t2.name from t1 JOIN t2 on t1.tl_alias = t2.alias, t1.tm_alias = t2.alias

Answer 1

使用内部联接和子查询

select t3.*,t2.name  from
(    
 select t1.alias,t2.name, t1.scores ,t1.tl_alias  from t1 join t2 on t1.alias =t2.alias
) as t3 join t2 on t3.tl_alias  =t2.tl_alias

或通过使用表别名将与t2的连接使用两次

select t1.alias,t2.name, t1.scores ,t1.tl_alias,t3.name 
 from t1 join t2 on t1.alias =t2.alias
      join t2 as t3 on t1.tl_alias=t3.alias

Answer 2

我在最初的评论中打错了口号，实际上您需要加入t2 3 次，就像这样...

SELECT t1.alias AS user_alias, t2_u.name AS user_name
   , t1.scores
   , t1.tl_alias, t2_l.name AS tl_name
   , t1.tm_alias, t2_m.name AS tm_name
FROM t1 
   JOIN t2 AS t2_u on t1.alias = t2_u.alias
   JOIN t2 AS t2_l on t1.tl_alias = t2_l.alias
   JOIN t2 AS t2_m ON t1.tm_alias = t2_m.alias
;

MySQL查询从多个表中获取数据

2 个答案: