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Question

I want to use select case for my prompts. Condition is that when the prompt :4 = 'I' then prompt :5 equals all of its values, and I use the code below but i receive the following error.

Error in running query because of SQL Error, Code=936, Message=ORA-00936: missing expression (50,380)

2 = 2 AND (CASE :5
WHEN :4 = 'I' AND :5 = ' ' 
THEN :5 = '%' 
END)

Anything wrong with my case statemnt?

Answer 1

There are two different syntaxes for CASE :

CASE value1
WHEN value2 THEN expression1
WHEN value2 THEN expression2
            ELSE expression3
END

and:

CASE
WHEN boolean_expression THEN expression1
WHEN boolean_expression THEN expression2
                        ELSE expression3
END

Note: The first statement can be converted to the second as

CASE
WHEN value1 = value2 THEN expression1
WHEN value1 = value3 THEN expression2
                     ELSE expression3
END

You are mixing these two syntaxes and it is invalid SQL.

You appear to want:

:5 = CASE WHEN :4 = 'I' AND :5 = ' ' THEN '%' END

However, even that will not work as bind variables are set once and are not re-evaluated so your logic would be:

   (     ( :4 = 'I' AND :5 = ' ' ) AND :5 = '%' )
OR ( NOT ( :4 = 'I' AND :5 = ' ' ) AND :5 = NULL )

Since :5 cannot ever be both ' ' and '%' then that branch of the logic can never be true and anything (including NULL ) is never equal to NULL so the second branch of the logic is also never true; therefore your expression will never match anything.

Answer 2

只需创建一个这样的表达式

decode(:4,'I',:5,SOMEVALUEORFIELD) = :5

Answer 3

This is your case expression:

(CASE :5 WHEN :4 = 'I' AND :5 = ' ' THEN :5 = '%' 
 END)

I cannot figure out what you really want. Both the CASE :5 and the :5 = '%' are improper. Perhaps:

(CASE WHEN :4 = 'I' AND :5 = ' ' THEN '%' 
 END) as :5

However, you don't normally use parameters for column aliases.