Unless the table is sparse. You would save one byte of storage per record if you changed from a nullable bit to a non nullable tinyint. As I see it there are two problems with your design. First you allow NULL to implicity have a value. You specify the value in your text as "maybe skipped". Also in surveys there is an option like "I don't want to answer this question". My experiense is that if you find yourself in the situation where NULL has a meaning you're doing something wrong.
It can be poor design, bad understanding of requirements or anyting else. In this case I wold propably have a lookup table with values "1:Yes, 2:No, 3:Skipped, 4:Don't want to answer".
This fast solution would also make it easy to insert the answer "Maybe" to the question "Do you want to whatever? For example "when was this invoice sent? Certainly many fields in tables will be NULL when their values are unknown. If the latter, consider the main premise of the article being about saving disk space by using the three possible values of a bit field.
I know a man who saved space in a bowling league Access database by storing scores range in a byte. By adding 45 when displaying and subtracting 45 when entering. That saved a byte per score. Over three games per person per week for the nine months of just for one league, that added up. If disk space is not an issue, then use tinyint. I am saying not to have any null fields.
But you will say, sometimes some attribute may be unknown but we want to create a record of what we do know. Fine, use a value to indicate the data is currently unknown. Or even better, move nullable columns into relations. When you have the the data for a column, add it to the relation. When no data, don't create a row in the relation.
Voila', no nulls needed. It might be worth thinking about why it is so tempting to try to use nulls to represent some consistent meaning in databases.
Note that I said "tempting", I did not say I think it is a good idea. Domains are definitions for allowable values, along with the operations allowable on those values. But as we all know, domains are not really supported in current implementations. Only pieces of the definition. Hence these recurring hassles trying to use them to represent business facts in an effiicent and reliable manner Let me try a fuller explanation.
The example query showed a literal NULL as part of the NOT IN list to illustrate the issue, hopefully that is not something any sane reader of this forum would actually do. The nullablility of the search field is beside the point. I posted what I thought was an absurd example, I never considered someone would try to fix it.
The list was the point of the example, not the search field. Changing the search field to ISNULL xyz, 'abc' or any other expression will have no effect on the results, but will probably cause the query optimizer to ignore any index on xyz and do a table scan. But that was not the original example query.
It does. When executed, the resultset will be all tables. Whether or not it's indexable is not my area of speciality, and I'll dig into it more.
It's useful to know. Based on the example in your latest post, I reckon the first query's IN clause started down a different path as the latter mentions a subquery rather than explicit values. It would be the subquery, then, that needs the ISNULL to return any static value to avoid the pitfall you've mentioned here.
For the Gender column, we can consider 1 as a male, for example, 0 as a female and NULL as unknown, undefined or other. With regard to the Test1Result, we can consider 1 as a positive and 0 as a negative. In terms of storage optimization, the main advantage is that if we have several Boolean columns, using bit type we can significantly reduce the space used.
As a simple example, we can use a table that stores the patients' several medical test results which are either positive or negative :. Here we have 8 columns of the bit data type and, therefore, 1 byte is used to store the values. If we used the tinyint or char 1 instead, 1 byte would be used for each of them. We can also derive benefits from using the bit data type in functions or stored procedures that accept or return Boolean values.
Let's assume we need a function that will check whether a patient is tested or not. Thus, we can use the bit data type as a return value type:. In conclusion, the bit data type can be quite useful if columns or variables accept only two values plus NULL. In these cases, using the bit type instead of the string or tinyint data types can make the code more logical and compact. Additionally, as SQL Server optimizes the storage of bit columns, the usage of this type can economically save storage, particularly if we have more than 8 columns of bit data type in the table.
Related Articles. Row sizes exceeding bytes in Sql Handling error converting data type varchar to numeric in SQL Server. SQL Server differences of char, nchar, varchar and nvarchar data types. Always use the right case for data type names in SQL Server. Can I actually set it to null? So the idea is something like this:. Could someone tell me if a table-valued parameter can be null?
As the User Define table Types are created as table-valued, so you cannot assign null to a table. I would like to check this for you, but I can't at the moment, but my gut feel is the same as twin. Basically you can't have a null table, but you can have an empty table.
From the front end i will pass the values but at times i may not send the values even though my Stored Procedure should accept the given parameters instead of arising the errors like expected input parameter skills. Here is an example for you. In this mode, It will insert into Employeeskill table if record exist in table values parameter.
If no record exist then it will not insert any record. You dont have to specify the default value for the table-valued parameter.
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