从多值列中查询不同的值

Question

我正在尝试查询“标签”列中的所有唯一值。 标签列中的每一行都可以包含多个值。 因此，如果不强制进入规范化，我如何查询多值列？

示例行：

Networking
Professionalism
Time Management
Communication, Networking
Career Management, Professionalism
Networking
Communication
Attitude, Interpersonal Skills, Professionalism
Business Protocol, Career Management, Communication, Leadership
Business Protocol, Networking

Answer 1

如果元素的最大数量是可预测的，您可以使用此功能（请注意，您需要使用UNION，而不是UNION ALL）

Select DISTINCT thefield from thetable where Instr(thefield, ',') = 0
UNION 
Select Distinct Mid(thefield, 1, Instr(thefield, ',')) from thetable Where len(thefield) - len(replace(thefield,',','')) = 1
UNION 
Select Distinct Mid(thefield, Instr(thefield, ',')+1) from thetable Where len(thefield) - len(replace(thefield,',','')) = 1
UNION 
Select Distinct Mid(thefield, Instr(thefield, ',')+1, Instr(Instr(thefield, ',')+1,thefield, ',')) from thetable Where len(thefield) - len(replace(thefield,',','')) = 2
UNION 
Select Distinct Mid(thefield, Instr(Instr(thefield, ',')+1,thefield, ',')+1) from thetable Where len(thefield) - len(replace(thefield,',','')) = 2
--.. and so on (repeat last two Selects as many time as you wish, increasing the where condition by one for each pair)

看起来有点笨重，但应该做的工作。未经测试，因此，您可能会在值

之前或之后出现迷路逗号