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Part of a complex query that our app is running contains the lines: ...(inner query)
SELECT ... NULL as column_A, NULL as column_B, ... FROM ... This syntax of creating columns with null values is not allowed in DB2 altough it is totally OK in MSSQL and Oracle DBs. Technically I can change it to:
'' as column_A, '' as column_B, But this doesn't have exactly the same meaning and can damage our calculation results. How can I create columns with null values in DB2 using other syntax??
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To test for the existence of nulls, use the special predicate IS NULL in the WHERE clause of the SELECT statement. You cannot simply state WHERE column = NULL. You must state WHERE column IS NULL. It is invalid to test if a column is <> NULL, or >= NULL.
The IS NULL condition is satisfied if the column contains a null value or if the expression cannot be evaluated because it contains one or more null values. If you use the IS NOT NULL operator, the condition is satisfied when the operand is column value that is not null, or an expression that does not evaluate to null.
If you have a column that does not allow the null value and you want to change it to now allow the null value, use the DROP NOT NULL clause. If you have a column that allows the null value and you want to prevent the use of null values, use the SET NOT NULL clause.
A null value is a special value that Db2 interprets to mean that no data is present. If you do not specify otherwise,Db2 allows any column to contain null values. Users can create rows in the table without providing a value for the column. Using the NOT NULL clause enables you to disallow null values in the column.
DB2 is strongly typed, so you need to tell DB2 what kind of column your NULL is:
select ... cast(NULL as int) as column_A, cast(NULL as varchar(128)) as column_B, ... FROM ... If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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