For my assignment I need help storing a boolean value that can hold yes or no. The column name is Required and the column attributes I received are Boolean value (1/0 or T/F) , Default value: NULL
I listed the sample data to be used bellow. The yes/no has to be stored without quotes somehow. Thank you
INSERT INTO CIS_Courses
VALUES ("CIS 105", "Computer Applications and Information Technology", null, Yes);
boolean data type is not available in sql server
you can use BIT datatype to represent boolean data.
A BIT field's value is either 1,0 or null
It also use the strings 'true' and 'false' in place of 1 or 0, like so-
declare #a bit = 'false'
print #a --output 0
declare #b bit = 'true'
print #b -- output 1
I always use tinyint(1) as boolean type value. Your table column would look like:
ColumnName tinyint(1) not null default 0
So when you don't insert a value, it will automatically be 0, or you can insert a 0 or 1.
I hope that this will help you
Related
I have a field that I want to convert to int so I can to a count, however some of the field's values are 'null' so I'm getting an exception when it comes across these
Conversion failed when converting the nvarchar value '_____' to data type int.
I thought id be able to do something like the below but I get the same result.
CAST( CASE [value] WHEN 'is null' THEN 1 ELSE [value] END AS INT)
I want to change all null values in [value] to 1 and then change all [value] to int so I can calculate this field.
You should have no issue converting a NULL value to an int, so I assume the issue is a string 'NULL'.
SQL Server offers TRY_CONVERT(). I recommend that you use that;
select try_convert(int, [value])
In other databases, you can use a regular expression to validate the data.
it will be is null that is not string
CAST( (CASE WHEN [value] is null THEN 1 ELSE [value] END) AS INT)
but its better to use try_convert what actually #Gordon recommend
Since you aren't actually looking for the NULL--which is the absence of data. You have bad data, i.e. the actual text 'NULL' in a column.
I would actually recommend you updating all the values to NULL so you can avoid doing try casting data to fix your problem. That would be something like:
UPDATE yourtable
SET [value] = NULL
WHERE [value] = 'NULL'
Then I would also change the column to a true INT type to avoid this in the future. But that's a bit outside the scope of your question.
Of course, you can't always change the data types. If you can, then this will be a more permanent solution.
How to return a default value when a column value is null in SQL
You can use COALESCE. Please refer https://www.sqlshack.com/using-the-sql-coalesce-function-in-sql-server/ for more info.
SELECT COALESCE (NULL,'A')
IsNull is used when the value is null and you want a default value to return.
Select IsNull(YourColumn, defaultvalue)
i.e.
Select IsNull( CandidateName , ''), -This is string column and return default value ''
IsNull(CandidateSalaryExpected, 0), --This is Integer/Double/Numeric column and return default value 0
IsNull(MaritalStatus , 0) --0 - marital means unmarried, 1 means married. This is boolean value
You can use Coalesce value too. Check the below link.
SQL Select Return Default Value If Null
Seems you are trying to fulfill your column with default value when any NULL value found.
You could try this:
SELECT COALESCE([dbo].YourTableName.[YourColumnName],'Default Value When Null Encountered') AS YourTableAlias FROM [dbo].[YourTable]
Test With Real Sample:
See my Table Column below where some FlatName is NULL
Real Query For Default Value When NULL Found:
SELECT FlatId,COALESCE([dbo].[Flat].[FlatName],'Default Value When Null Encountered') AS FlatName, FlatDescription FROM [dbo].[Flat]
Output Of Query:
Instead of returning default value, you can design your table to add default value if the value is not provided. See below example
CREATE TABLE DemoTable
(
ID INT,
Name VARCHAR(100),
RecordAddedOn DATETIME DEFAULT GETDATE()
)
You cane take a look at below link to have a better idea about default constraint. Default Constraint
However, if you want to return default value, you can use ISNULL(ColumnName, ‘Default Value’)
I am trying to create table in SQL Developer but I did not find the Boolean data type or bit data type.
Is their another type instead of these?
Oracle doesn't support a Boolean datatype for columns. A common work-around is VARCHAR2(1) or char with a constraint to permit only 'Y' and 'N'' as values.
if you want to create table with bool column, here the sample syntax
create table boolTable (
bool char check (bool in ('N','Y')
));
insert into boolTable values('Y'); -- This query insert value
`insert into boolTable values(1);` -- This query going to fail.
A Bit in SQL can be sequence of zeros and ones and not only just 0 or 1 as true or false.
It can be 0, 1, 00000, 1111, 0101010, 000111.. etc.
To create a boolean, u can use TINYINT(1)
My curiosity always gets the best of me and I've searched online for an explanation to this and came up with nothing (could be because I didn't use the right terms.)
Can someone please explain why SQL Server returns a value of zero (0) when the following is executed, instead of an empty string ('').
DECLARE #I AS INT
SET #I = NULL
SELECT ISNULL(#I, '') -- 0
As declared here, the second argument to ISNULL is the replacement_value, which "must be of a type that is implicitly convertible to the type of check_expresssion." Implicitly converting '' to INT results in 0.
Because #I is declared as an INT, the empty string is implicitly CAST as an integer resulting in a ZERO.
I know is an old question, but I want to share.
The issue here is not because the casting of the ' ' expression, is because the int data type is not null-able and, when you try to SET #I = NULL SQL set the default value zero(0).
That's why the statement ISNULL(#I, '') does not find any null in #I and returns its value(0).
Hope it helps somebody out there.
Please suppose that in SQL Server 2005, if you launch the following query:
SELECT CHICKEN_CODE FROM ALL_CHICKENS WHERE MY_PARAMETER = 'N123123123';
you obtain:
31
as result.
Now, I would like to write a function that, given a value for MY_PARAMETER, yields the corresponding value of CHICKEN_CODE, found in the table ALL_CHICKENS.
I have written the following stored function in SQL Server 2005:
ALTER FUNCTION [dbo].[determines_chicken_code]
(
#input_parameter VARCHAR
)
RETURNS varchar
AS
BEGIN
DECLARE #myresult varchar
SELECT #myresult = CHICKEN_CODE
FROM dbo.ALL_CHICKENS
WHERE MY_PARAMETER = #input_parameter
RETURN #myresult
END
But if I launch the following query:
SELECT DBO.determines_chicken_code('N123123123')
it yields:
NULL
Why?
Thank you in advance for your kind cooperation.
define the length of your varchar variables like this
varchar(100)
Without the 100 (or whatever length you choose) its lengh is 1 and the where clause will filter out the correct results.
Specify a length for your varchar (ex.: varchar(100)). Without length, varchar = 1 char.
As per other PS, You can store only one char in the #myresult because you have not specified any length, bcoz 1 char length is default for Varchar datatype.
Why we are getting NUll, not the first char:
If there are multiple records are filtered on basis of Where clause in ALL_CHICKENS table then the value of CHICKEN_CODE column is picked up from last row in ALL_CHICKENS table.
It seems that the last row has null value in CHICKEN_CODE column.
Specify a length for #input_parameter, #myresult as by default varchar lengh is 1.