select from table where column = anything

Question

A simplified example of what I need:

Table 'Transport' has 2 columns; 'Vehicle' and 'Colour'. User can filter records by either a vehicle, a colour, or both.

variable vehicle_choice = user_selected_vehicle (selected from a dropdown for example)
variable colour_choice = user_selected_colour

If user_selected_vehicle = nothing selected Then
    vehicle_choice = *
End if

If user_selected_colour = nothing selected Then
    colour_choice = *
End if

Select query = ("Select * From Transport Where Vehicle = vehicle_choice And Colour = colour_choice")

So if the user wanted a 'red' 'bus' the query would look like:

("Select * From Transport Where Vehicle = 'bus' And Colour = 'red'")

Which would be fine and find the record if it existed.

But, if the user wanted all vehicles that were yellow the query would look like:

("Select * From Transport Where Vehicle = * and Colour = 'yellow'")

Clearly this is all in a made up syntax but this is what I want, is it possible in SQL? (Using MS SQL Server 2008)

Answer 1

Here are two typical ways to solve this. Assume that the user input is in the variables @vehicle and @colour :

where (vehicle = @vehicle or @vehicle is null) and
      (colour = @colour or @colour is null)

The problem with this approach is the use of indexes. Indexing strategies have a hard time with or . So, if you are constructing the query dynamically, then it is better to only add the clauses you want:

@where = '1 = 1' +
         (case when @vehicle is not null then ' and vehicle = @vehicle' else '' end) +
         (case when @colour is not null then ' and colour = @colour' else '' end);

Answer 2

您可以尝试类似

("Select * From Transport Where Vehicle like '%' and Colour = 'yellow'")

Answer 3

You can prepare 2nd query

("Select * From Transport Where Vehicle = * and Colour = 'yellow'")

to this

("Select * From Transport Where Vehicle = Vehicle and Colour = 'yellow'")

It's only idea how to solve your problem.

Answer 4

Yes. it is possible.just modify your query like this:

suppose your dropdown parameter is:

ddl1.val -- for transport
ddl2.val -- for color

now suppose your default ddl values is '0' or whatever for 'select all' option.now your query will be:

 Select * From Transport Where (Vehicle = ddl1.val or ddl1.val='0') and
(Colour = ddl2.val or ddl2.val='0')

alternate way to do this:

Select * From Transport Where Vehicle like '%' and Colour = 'color_selected'

let me know if u want any other clarification regarding this.

Answer 5

declare @vehicle_choice nvarchar(255)
declare @colour_choice nvarchar(255)
set @colour_choice = 'bus'
set @colour_choice = 'blue'

Select * From Transport 
    where 1= 1 
    and Vehicle like (case when @vehicle_choice Is null or @vehicle_choice = '' then '%' else @vehicle_choice end)
    and Colour like (case when @colour_choice Is null or @colour_choice = '' then '%' else @colour_choice end)