mysql - 仅两个表之间的多重联接

Question

表1:key_item#、code_1、code_2、code_3

表2:uniq_code、code_desc

表1:

key_item#  code_1  code_2  code_3
   1         Y01    M02     X01
   2         Y01    M04     X01

表2:

uniq_code      code_desc
   Y01       DescriptionY01
   M02       DescriptionM02
   X01       DescriptionX01
   M04       DescriptionM04

更好的图像细节 https://dl.dropboxusercontent.com/u/9951225/Untitled-4.jpg

查询结果

key_item#   code_1     code_desc      code_2        code_desc    cod_3    code_desc
   1          Y01    DescriptionY01     M02     DescriptionM02    X01   DescriptionX01
   2          Y01    DescriptionY01     M04     DescriptionM04    X01   DescriptionX01

查询

SELECT     Table1.key_item#,
           Table1.code_1,
           Table2.code_desc,
           Table1.code_2,
           Table2.code_desc, 
           imc_iamerican_claim_lines.Add_diagnosis1 

FROM       msp_dx9_priority.dx09code_matrix 
INNER JOIN Table1 ON Table1.code_1 = Table2.uniq_code 
INNER JOIN Table1 ON Table1.code_2 = Table2.uniq_code

我无法解决“表别名不唯一”错误

Answer 1

您需要为联接添加别名，以便查询引擎知道如何消除第一个 Table1 和第二个 Table1 的歧义。此处的文档:http://dev.mysql.com/doc/refman/5.0/en/join.html

这是一个例子:

SELECT     Table1.key_item#, -- which join should this come from? code1 or code2?
           t1_code1.code_1,
           Table2.code_desc, -- don't know what is Table2, perhaps t1_code1?
           t1_code2.code_2,
           Table2.code_desc, -- don't know what is Table2, perhaps t1_code2?
           imc_iamerican_claim_lines.Add_diagnosis1  -- also don't know what this is :)

FROM       msp_dx9_priority.dx09code_matrix 
INNER JOIN Table1 t1_code1 ON t1_code1.code_1 = Table2.uniq_code 
INNER JOIN Table1 t1_code2 ON t1_code2.code_2 = Table2.uniq_code