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Improve this answer. Larry Coleman Larry Coleman 1, 16 16 silver badges 8 8 bronze badges. I try to reserve NULL for 'not known' It's particularly useful for when your data comes from multiple sources — Joe. Larry what's the performance impact? How does the performance vary with tables of many cols vs.
I agree that if there is a distinction between no value given and an empty string in your dataset then you should use them appropriately, but personally if I don't need that distinction with my data then I always use an empty string, purely because I find that query result from a MySQL client on the command line can be cleaner to look at with empty strings instead of lots of NULLs — RTF.
And you have to worry whether trimming not empty results in NULL select case when ltrim ' ' is null then 'null' else 'not null' end from dual It does. SQL-Server Working with '' is generally easier and in most case there is no practical need to distinguish between both. T-Gergely 2 2 bronze badges. Gan Gan 6 6 silver badges 15 15 bronze badges. If the user chose not to provide a gender, surely you should store "Declined to provide".
NULL is ambiguous; it could also mean "the customer has not been asked", "the customer identifies with a gender not on our list", etc. Matthew Schinckel Matthew Schinckel 1 1 silver badge 4 4 bronze badges. It is actually not the case that NULL! Fortunately, starting with you can use a filtered index to get proper behavior. Community Bot 1. Abie Abie 8 8 silver badges 9 9 bronze badges. Patrick Patrick 4, 7 7 gold badges 26 26 silver badges 26 26 bronze badges.
They are also different from a design perspective: e. Soooooo: nulls are not trivial strings nor the reverse. Guy Birkbeck Guy Birkbeck 86 1 1 bronze badge.
That's PostGres. As other posters noted, in Oracle there is no difference. Having had to work with Oracle which doesn't allow you to differentiate I have come to the following conclusion: From a logical POV it doesn't matter. Martin Martin 2, 4 4 gold badges 22 22 silver badges 34 34 bronze badges. Chances are that a person said something non empty string a person said nothing empty string you don't know what a person said null value You can make your data mean what is more convenient to you by exploting or not what is offered to you.
Riccardo Manfrin Riccardo Manfrin Slartibartfast Slartibartfast 9 2 2 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Stack Gives Back As you can see , PhoneNo1 length in bytes is still null means memory is not allocated to it yet which means that it is unknown value, while phoneNo2 length is zero 0 , that means memory is allocated to empty field. This site uses Akismet to reduce spam.
Learn how your comment data is processed. Lets look at the difference between Null and Empty as given below: Null can be a unknown value or an absence of a value, where as an Empty or Blank string is a value, but is just empty. Null can be used for string , Integer ,date , or any fields in a database where as Empty is used for string fields.
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