SQL nvl equivalent - without if/case statements & isnull & coalesce

Question

Are there any nvl() equivalent functions in SQL?

Or something close enough to be used in the same way in certain scenarios?

---

UPDATE:
no if statements
no case statements
no isnull
no coalesce

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select nvl (purge_date,"SODIUFOSDIUFSDOIFUDSF") from id_rec where id=36581;


(expression)

SODIUFOSDIUFSDOIFUDSF

1 row(s) retrieved.

select isnull (purge_date,"SODIUFOSDIUFSDOIFUDSF") from id_rec where id=36581;

  674: Routine (isnull) can not be resolved.
Error in line 1
Near character position 8

select coalesce (purge_date,"SODIUFOSDIUFSDOIFUDSF") from id_rec where id=36581;

  674: Routine (coalesce) can not be resolved.
Error in line 1
Near character position 8

select decode(purge_date, NULL, "01/01/2009", purge_date) from id_rec where id=74115;

  800: Corresponding types must be compatible in CASE expression.
Error in line 1
Near character position 57

Solution 1

You seem to be using Informix.

AFAIK, there is DECODE there:

DECODE(field, NULL, 'it is null, man', field) should give you same result as NVL(field, 'it is null, man')

Please post exact name and version of the RDBMS you are using.

Solution 2

ISNULL (for a single replace)

or

COALESCE (Returns the first nonnull expression among its arguments.)

Solution 3

SQL Server: IsNull or COALESCE http://msdn.microsoft.com/en-us/library/ms184325.aspx

Sybase: isnull function http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.help.ase_15.0.blocks/html/blocks/blocks162.htm

Postgres: I couldn't find one though haven't fully checked. Suggests to select where IS NULL and build from here http://archives.postgresql.org/pgsql-sql/1998-06/msg00142.php

DB2 - COALESCE http://publib.boulder.ibm.com/infocenter/db2luw/v8/index.jsp?topic=/com.ibm.db2.udb.doc/admin/r0000780.htm

Solution 4

The problem with your DECODE statement that is generating the 800 error is simple. '01/01/2009' is being treated as a string, and it's actually the 4th argument that generates the error.

Appreciate that the input and output of a DECODE statement can be different data-types, so the engine requires you to be more explicit in this case. (Do you want purge_date cast as a string or the string '01/01/2009', or the string argument parsed as a date or the original date? There's no way for the engine to know.

Try this:

SELECT DECODE(purge_date, NULL, '01/01/2009'::DATE, purge_date)

You could also write that 3rd argument as:

    DATE('01/01/2009')
    MDY(1,1,2009)

depending on version and personal preference.

View more solutions

Comments

[topski]

Exact version you are using would be helpful. Also, if nvl works, why not use it?

[CheeseConQueso]

I'm not sure how to find out which version im using.. its informix and its old... for one scenario nvl issn't working and i don't know why

[topski]

What's the scenario that NVL is causing a problem?

[CheeseConQueso]

There is a field in one of my tables that is 'null' ("" or " ") and its supposed to be the name of someone. We set one key up for general usage and never put a name in. It finally hit the fan and I had to fix it, but NVL didnt do it, I had to get around it with a bunch of BS

[Jonathan Leffler]

Don't forget that unlike some other systems, Informix does not treat an empty string as NULL - the two are different. Running an Informix program with the '-V' option should print some version information. The name of the program you chose might help, too.

[Jonathan Leffler]

Consequently, what you probably need is a condition WHERE somecolumn = ' ' or an equivalent (any number of spaces, including zero, is OK; you can use double quotes instead of single quotes, too).

[CheeseConQueso]

Yea, old informix.. dont know what version... i got this error from that syntax select decode(purge_date, NULL, "01/01/2009", purge_date) from id_rec where id=74115; 800: Corresponding types must be compatible in CASE expression. Error in line 1 Near character position 57

[Kenny Drobnack]

I'm working on Sybase 12.5. Neither DECODE nor NVL are available but ISNULL worked great.

[TWiStErRob]

DECODE is working nice, but the date you're trying to give is a string, or with implicit conversion I guess it's datetime year to second or whatever the default is. So use DECODE(purge_date, NULL, EXTEND('01/01/2009', year to day), purge_date) from id_rec to convert to purge_date's format. (Just noticed, the same explanation is down below in @RET's answer)