仅两个表之间的多个联接

Question

Table1: key_item#, code_1, code_2, code_3

Table2: uniq_code, code_desc

Table1:

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

Table2:

uniq_code      code_desc
   Y01       DescriptionY01
   M02       DescriptionM02
   X01       DescriptionX01
   M04       DescriptionM04

Better image detail https://dl.dropboxusercontent.com/u/9951225/Untitled-4.jpg

Query Result

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

Query

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

I can't go over the "Not unique table Alias" error

Answer 1

You need to alias your joins, so that the query engine knows how to disambiguate the first Table1 from the second Table1. Documentation here: http://dev.mysql.com/doc/refman/5.0/en/join.html

Here is an example:

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

Answer 2

I found this approach

 SELECT t1.key, t1.code_1, t21.`desc` as desc_1, t1.code_2, t22.`desc` as desc2, t1.code_3, t23.`desc` as desc3 FROM t1 LEFT JOIN t2 t21 on t1.code_1 = t21.code LEFT JOIN t2 t22 ON t1.code_2 = t22.code LEFT JOIN t2 t23 ON t1.code_3 = t23.code; 

With this reference I did my final report. Just in case someone is going to need it.