从SQL结果中排除项目

Question

I may be missing something because I thought this would be a simple task.

I wanted to retrieve results that were not included in Table 3.

Any help?

Table 1

T1C1  T1C2   

  1     London
  2     New York
  3     Paris
  4     Cardiff  
  5     Bradford
  6     Sydney
  7     Bradford
  8     Beijing
  9     Cairo

Table 2

T2C1  T2C2   

  A     UK

Table 3

T3C1  T3C2   

  1     A
  4     A 
  5     A
  7     A

Result

T1C1  T1C2   

  2    New York
  3    Paris
  6    Sydney
  8    Beijing
  9    Cairo

Answer 1

1. select * from Table1 where T1C1 not in (select T3C1 from Table3)
2. select * from Table1 left join Table2 on T1C1=T3C1 where T3C2 IS NULL
3. select * from Table1 where not exists (select 1 from Table2 where T1C1=T3C1) （由Tim Schmelter在评论中建议）

Answer 2

You could just use NOT IN;

SELECT * FROM Table1 WHERE T1C1 NOT IN (
   SELECT T1C1 FROM Table3
)