Sql-server – Concatenate with NULL values ( Should not replace NULL )

nullsql serversql-server-2008-r2string manipulation

After some time searching for an answer, I got a LOT of question saying to use coalesce,concat(), and etc, but what I need is:

Table:

create table nulos ( nome varchar(max))
alter table nulos add cidade varchar(max)

values:

insert into nulos values ( 'rafael','são paulo'),('juliana',null)

I need to concatenate the values inside this table, to a insert, like this:

 select 'insert into nulos (nome,cidade) values ('+nome+','+cidade+')'
from nulos

And the result of the select:

insert into nulos (nome,cidade) values (rafael,são paulo)
NULL

how can I use the NULL value inside this concatenation? every answer says something to replace the null with '' or '_', But what I need it this:

insert into nulos (nome,cidade) values (rafael,são paulo)

insert into nulos (nome,cidade) values (Juliana,NULL)

SET CONCAT_NULL_YIELDS_NULL on is not an option because it just deletes the NULL value, and I need to insert it.

Best Answer

Wrap your strings in single quotes so they will be input as strings. The NULL does not need quotes.

SELECT 'INSERT INTO nulos (nome,cidade) VALUES (' +
    CASE WHEN nome is null then 'NULL' ELSE ''''+
        REPLACE(nome,'''','''''')+'''' END + 
    ',' +
    CASE WHEN cidade is null then 'NULL' ELSE ''''+
        REPLACE(cidade,'''','''''')+'''' END +
    ')'
FROM nulos

This will give you:

INSERT INTO nulos (nome,cidade) VALUES ('rafael','são paulo')
INSERT INTO nulos (nome,cidade) VALUES ('Juliana',NULL)

Related Solutions

Sql-server – Should I convert empty varchar values to NULL

As a DBA, your sacred duty is to take whatever data was entrusted to you, and leave it as is.

A NULL in a field usually means "DATA was not entered" or "DATA is not applicable" (but can have other meanings - it is context specific), and may actually MEAN something to the business layer. An empty string may actually be what the user entered and WANTS. Of course, I am generalizing - possibly the reason you get either NULLs or '' (empty strings) is due to some sloppy coding in the business layer (let us hope not, though).

Either way, have a chat with whoever provides the Middle Tier and see what they are using NULL vs Empty String for - and then go from there. Maybe they are thinking that they always pass in an Empty String (or always NULLS) and are not aware of the randomness (in which case advise them on what you think should be the standard), or maybe NULL really is information to them

Postgresql – Select query to retrieve rows with null values

This example retrieves only "name" and the "SUM(credit)", when the "credit" has values.

The query you presented will retrieve a row for every present name, even if all associated credit columns are NULL. You get a row with a NULL value for SUM(credit) then. Null values are just ignored by the aggregate function sum():

You only get no row for a particular name if no row for that name exists in the table expenses for the given WHERE expressions.

I am assuming you want
.. only names matching 'vendor0%'
.. but all of those, even if they have no expenses in 2013.

Your query could work like this:

SELECT name, SUM(CASE WHEN date LIKE '2013%' THEN credit END) AS credit
FROM   expenses
WHERE  name LIKE 'vendor0%'
GROUP  BY name
ORDER  BY name

CASE defaults to NULL if no ELSE branch is given.
Aside: You shouldn't store date / time values as text. Use an appropriate type, it has many advantages.
And don't use "name" or "date" as identifiers. "name" is not a descriptive name and "date" is a reserved word in standard SQL and a function and base type name in Postgres.

Best Answer

Related Solutions

Sql-server – Should I convert empty varchar values to NULL

Postgresql – Select query to retrieve rows with null values

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