Case When to check if is null

Question

I have a filter for the clients for a report, if the person put the filter Client it uses,else it ignores and bring all clients. This is my Where clause.

Where [S].ano_mes = @ano_mes OR @ano_mes IS NULL    
            AND S.cnpj = @cnpj or @cnpj is null     
            AND S.cod_produto = @cod_produto or @cod_produto is null    
            AND CASE WHEN (len(@cnpj) > 0) THEN 
                 (S.CGC_Cliente +''-''+S.Seq_Cliente) in(SELECT cnpjseq FROM #Tb_CliSelecionados)
                    END

The problem is in the CASE WHEN part,the rest works.

If the variable @cnpj has value THEN it should use the filter.

The filters is CGC_CLIENTE and SEQ_CLIENTE together.

The table #Tb_CliSelecionados has the parameters Concatenated equals,exemple,both the table with alias S and #Tb_CliSelecionados has '060746948041730-00'

i'm getting erro in two parts in the "IN" its says incorrect syntax near "IN" And in the END saying incorrect syntax near "END".Expection ")"

Someone knows what i'm doing wrong in the case when part?

Answer 1

CASE return one expresion isn't a flow control.

 AND CASE WHEN len(@cnpj) IS NULL 
               THEN 1
          WHEN (len(@cnpj) > 0) 
               THEN  CASE WHEN exists
                           (SELECT 1 
                            FROM #Tb_CliSelecionados
                            WHERE cnpjseq = S.CGC_Cliente +''-''+ S.Seq_Cliente )
                          THEN 1 -- if exist the match return the row
                          ELSE 0 -- other wise ignore the row
                     END
         ELSE 1 -- if len(@cnpj) == 0 then return all rows
     END = 1  -- HERE YOU return the row if CASE return 1

Answer 2

The CASE WHEN clause is incorrect. It should look like:

         AND CASE 
             WHEN @cnpj IS NULL
                 THEN 1
             WHEN (len(@cnpj) = 0) 
                 THEN 1
             WHEN (S.CGC_Cliente +''-''+S.Seq_Cliente) in (SELECT cnpjseq FROM #Tb_CliSelecionados
                 THEN 1
             ELSE 0
         END = 1

Answer 3

You can change that part to

AND ( len(@cnpj) > 0
       AND S.CGC_Cliente + '-' + S.Seq_Cliente in (SELECT cnpjseq FROM #Tb_CliSelecionados))