How come string can contain integer. Even if I assume string storing numeric values as string, but even i can use in it calculation and getting the result as well. Just to try I wrote 5 in inverted commas and still calculation works fine. Not sure how?
declare #x varchar(20)
declare #y int
select #x='5'
select #y=6
select #x+#y
SQL Server -- and all other databases -- convert values among types when the need arises.
In this case, you have + which can be either string concatenation or number addition. Because one argument is an integer, it is interpreted as addition, and SQL Server attempts to convert the string to a number.
If the string cannot be converted, then you will get an error.
I would advise you to do your best to avoid such implicit conversions. Use the correct type when defining values. If you need to store other types in a string, use cast()/convert() . . . or better yet, try_cast()/try_convert():
try_convert(int, #x) + #y
A varchar can contain any character from the collations codepage you are using. For the purposes of this answer, I'm going to assume you're using something like the collation SQL_Latin1_General_CP1_CI_AS (which doesn't have any "international" characters, like Kanji, Hiragana, etc).
You first declare the variable #x as a varchar(20) and put the varchar value '5' in it. This is not an int, it's a varchar. This is an important distinction as a varchar and a numerical data type (like an int) behave very differently. For example '10' has a lower value than '2', where as the opposite is true for 10 and 2. (This is one reason why using the correct data type is always important.)
Then the second variable you have is #y, which is an int and has the value 6.
Then you have your expression SELECT #x+#y;. This has 2 parts to it. Firstly, as you have 2 datatypes, Data Type Precedence comes into play. int has a higher precedence than a varchar, and so #x is implicitly converted to an int. Then the expression is calculated, uses + as an addition operator (not a concatenation operator). Therefore the expression is effectively derived like this:
#x + #y = '5' + 6 = CONVERT(int,'5') + 6 = 5 + 6 = 11
SQL Server uses the following precedence order for data types:
user-defined data types (highest)
sql_variant
xml
datetimeoffset
datetime2
datetime
smalldatetime
date
time
float
real
decimal
money
smallmoney
bigint
int
smallint
tinyint
bit
ntext
text
image
timestamp
uniqueidentifier
nvarchar (including nvarchar(max) )
nchar
varchar (including varchar(max) )
char
varbinary (including varbinary(max) )
binary (lowest)
Related
Just need your help here.
I have a table T
A (nvarchar) B()
--------------------------
'abcd'
'xyzxcz'
B should output length of entries in A for which I did
UPDATE T
SET B = LEN(A) -- I know LEN function returns int
But when I checked out the datatype of B using sp_help T, it showed column B as nvarchar.
What's going on ?
select A
from T
where B > 100
also returned correct output?
Why is nvarchar working with logical operators ?
Please help.
Check https://learn.microsoft.com/en-us/sql/t-sql/data-types/data-type-conversion-database-engine?view=sql-server-2017 where it is said that data types are converted explicitly or implicitly when you move, compare or store a variable. In your case, you are comparing column B with 100, forcing sql server to implicitly convert it to integer type (check the picture about conversions on the same page). As a prove, try to alter a row putting some text in column B and, after repeating your select query B>100, sql server will throw a conversione error trying to obtain an integer out of your text.
It works because of implicit conversion between types.
Data type precedence
When an operator combines expressions of different data types, the data type with the lower precedence is first converted to the data type with the higher precedence. If the conversion isn't a supported implicit conversion, an error is returned.
Types precedence:
16. int
...
25. nvarchar (including nvarchar(max) )
In you example:
select A
from T
where B > 100
--nvarchar and int (B is implicitly casted to INT)
when adding a column to a table in ssms, not adding a datatype a "default" datatype is chosen. for me on 2017 developer it's nchar(10). if you want it to be int define the column with datatype of int. in tsql it'd be
create table T (
A nvarchar --for me the nvarchar without a size gives an nvarchar(2)
,B int
);
sp_help T
--to make a specific size, largest for nvarchar is 4000 or max...max is the replacement for ntext of old, as.
create table Tmax (
A nvarchar(max)
,B int
);
--understanding nvarchar and varchar for len() and datalength()
select
datalength(N'wibble') datalength_nvarchar -- nvarchar is unicode and uses 2 bytes per char, so 12
,datalength('wibble') datalength_varchar -- varchar uses 1 byte per so 6
,len(N'wibble') len_nvarchar -- count of chars, so 6
,len('wibble') len_varchar -- count of char so still 6
nvarchar(max) and varchar(max)
hope this helps, the question is a bit discombobulated
Is it possible to convert a varchar(10) into an int in SQL Server 2014?
I tried the following code, but I get a conversion error
Declare #Random varchar(10)
set #Random = CONVERT(varchar, right(newid(),10))
Declare #rand int = cast(#Random as int)
select #rand
Is it possible to convert a varchar(10) into an int under SQL Server 2012?
Yes, if the varchar(10) string is all numeric characters and the string is within the bound of an int:
-2^31 (-2,147,483,648) to 2^31-1 (2,147,483,647)
In other words, this will work:
select cast('2147483647' as int)
This will not:
select cast('2147483648' as int)
I tried the following code, but I get a conversion error
The code in your question isn't testing whether you can convert a string to an integer, it is testing whether any random string can be converted. Your random strings contain alpha characters that cannot convert to an integer so you are getting conversion errors. But even if you limit the random string to numbers, you will still only be able to convert numeric strings up to 2147483647 before you overflow your int. I don't think that generating (not-so) random strings that meet this criteria will prove much. The simple answer to your question is yes, you can convert a string to an int, as long as the string meets the requirements of an int.
You could try:
SELECT TRY_CAST(RIGHT(CAST(convert(VARBINARY, NEWID(), 1) AS BIGINT),10) AS INT);
Rextester Demo
Or if you use only 9 digitis:
SELECT RIGHT(CAST(convert(VARBINARY, NEWID(), 1) AS BIGINT),9) + 0;
Ignore the practicality of the following sql query
DECLARE #limit BIGINT
SELECT TOP (COALESCE(#limit, 9223372036854775807))
*
FROM
sometable
It warns that
The number of rows provided for a TOP or FETCH clauses row count parameter must be an integer.
Why doesn't it work but the following works?
SELECT TOP 9223372036854775807
*
FROM
sometable
And COALESCE(#limit, 9223372036854775807) is indeed 9223372036854775807 when #limit is null?
I know that changing COALESCE to ISNULL works but I want to know the reason.
https://technet.microsoft.com/en-us/library/aa223927%28v=sql.80%29.aspx
Specifying bigint Constants
Whole number constants that are outside the range supported by the int
data type continue to be interpreted as numeric, with a scale of 0 and
a precision sufficient to hold the value specified. For example, the
constant 3000000000 is interpreted as numeric. These numeric constants
are implicitly convertible to bigint and can be assigned to bigint
columns and variables:
DECLARE #limit bigint
SELECT SQL_VARIANT_PROPERTY(COALESCE(#limit, 9223372036854775807),'BaseType')
SELECT SQL_VARIANT_PROPERTY(9223372036854775807, 'BaseType') BaseType
shows that 9223372036854775807 is numeric, so the return value of coalesce is numeric. Whereas
DECLARE #limit bigint
SELECT SQL_VARIANT_PROPERTY(ISNULL(#limit, 9223372036854775807),'BaseType')
gives bigint. Difference being ISNULL return value has the data type of the first expression, but COALESCE return value has the highest data type.
SELECT TOP (cast(COALESCE(#limit, 9223372036854775807) as bigint))
*
FROM
tbl
should work.
DECLARE
#x AS VARCHAR(3) = NULL,
#y AS VARCHAR(10) = '1234567890';
SELECT
COALESCE(#x, #y) AS COALESCExy, COALESCE(#y, #x)
AS COALESCEyx,
ISNULL(#x, #y) AS ISNULLxy, ISNULL(#y, #x)
AS ISNULLyx;
Output:
COALESCExy COALESCEyx ISNULLxy ISNULLyx
---------- ---------- -------- ----------
1234567890 1234567890 123 1234567890
Notice that with COALESCE, regardless of which input is specified first, the type of the output is VARCHAR(10)—the one with the higher precedence. However, with ISNULL, the type of the output is determined by the first input. So when the first input is of a VARCHAR(3) data type (the expression aliased as ISNULLxy), the output is VARCHAR(3). As a result, the returned value that originated in the input #y is truncated after three characters.That means isnull would not change the type, but coalesce would.
Turns out that 9223372036854775807 is a numeric instead of a bigint
From https://technet.microsoft.com/en-us/library/aa223927(v=sql.80).aspx
Whole number constants that are outside the range supported by the int data type continue to be interpreted as numeric, with a scale of 0 and a precision sufficient to hold the value specified
So we need to explicitly cast it to bigint
DECLARE #limit BIGINT
SELECT TOP (COALESCE(#limit, CAST(9223372036854775807 AS BIGINT)))
*
FROM
sometable
If in a SELECT statement there is the following line:
iif(fr.BoundID=0,'OutBound','InBound') as 'FlightBound'
Then when I perform a CREATE TABLE statement, should I include the actual datatype of the BoundID field which is a tinyint in the database table, or shall the datatype be varchar because I think (but not 100% sure looking at the existing code) that the previous person writing this code is saying display 'OutBound, InBound' if the ID is 0?
In your case it will be VARCHAR(8). You can always check metadata using sys.dm_exec_describe_first_result_set:
SELECT *
FROM sys.dm_exec_describe_first_result_set(
'SELECT iif(BoundID=0,''OutBound'',''InBound'') as ''FlightBound''
FROM #tab',NULL,0)
LiveDemo
What datatype to choose for new table TINYINT vs Textual representation is dependent on your business requirements. I would probably stay with TINYINT (search for lookup table named like BoundType or ask senior developer/architect).
The return type is the type in true_value and false_value with the highest precendence (reference, see return types)
Returns the data type with the highest precedence from the types in true_value and false_value. For more information, see Data Type Precedence (Transact-SQL).
Data type precendence here up to SQL Server 2016:
user-defined data types (highest)
sql_variant
xml
datetimeoffset
datetime2
datetime
smalldatetime
date
time
float
real
decimal
money
smallmoney
bigint
int
smallint
tinyint
bit
ntext
text
image
timestamp
uniqueidentifier
nvarchar (including nvarchar(max) )
nchar
varchar (including varchar(max) )
char
varbinary (including varbinary(max) )
binary (lowest)
I have a SQL function with following signature
(
#value as VARCHAR(MAX)
)
RETURNS NCHAR(47)
What will happen if the input of the function will be int?
Implicit casting to VARCHAR(MAX)?
i.e if the input is int 12 how will it be transferred to the function input leading zeros and 12 - "000000..000012"
It gets cast to varchar but there will be no leading 0's, it will simply be read as 12. Just because you specify varchar(max) doesn't mean it will use the space it has and automatically fill it with 0's.