Is there a way to make a column have a contraint of exactly so many characters? I have a string of 152 characters, and want the column to only accept values that are 152 in length, not 151, not 153. I know char can handle the overflow, but what about the minimum version?
Add a check constraint which asserts that the length of the incoming string is exactly 152 characters:
ALTER TABLE [dbo].[YourTable] WITH CHECK
ADD CONSTRAINT [cnstr] CHECK (LEN(LTRIM([col])) = 152);
Related
I would like to check if a specific column in one of my tables meets the following conditions:
String must contain at least three characters
String must contain at least two different numbers [e.g. 123 would work but 111 would not]
Characters which are allowed in the string:
Numbers (0-9)
Uppercase letters
Lowercase letters
Underscores (_)]
Dashes (-)
I have some experience with Regex but am having issues with Snowflake's syntax. Whenever I try using the '?' regex character (to mark something as optional) I receive an error. Can someone help me understand a workaround and provide a solution?
What I have so far:
SELECT string,
LENGTH(string) AS length
FROM tbl
WHERE REGEXP_LIKE(string,'^[0-9]+{3,}[-+]?[A-Z]?[a-z]?$')
ORDER BY length;
Thanks!
Your regex looks a little confusing and invalid, and it doesn't look like it quite meets your needs either. I read this expression as a string that:
Must start with one or more digits, at least 3 or more times
The confusing part to me is the '+' is a quantifier, which is not quantifiable with {3,} but somehow doesn't produce an error for me
Optionally followed by either a dash or plus sign
Followed by an uppercase character zero or one times (giving back as needed)
Followed by and ending with a lowercase character zero or one times (giving back as needed)
Questions
You say that your string must contain 3 characters and at least 2 different numbers, numbers are characters but I'm not sure if you mean 3 letters...
Are you considering the numbers to be characters?
Does the order of the characters matter?
Can you provide an example of the error you are receiving?
Notes
Checking for a second digit that is not the same as the first involves the concept of a lookahead with a backreference. Snowflake does not support backreferences.
One thing about pattern matching with regular expressions is that order makes a difference. If order is not of importance to you, then you'll have multiple patterns to match against.
Example
Below is how you can test each part of your requirements individually. I've included a few regexp_substr functions to show how extraction can work to check if something exists again.
Uncomment the WHERE clause to see the dataset filtered. The filters are written as expressions so you can remove any/all of the regexp_* columns.
select randstr(36,random(123)) as r_string
,length(r_string) AS length
,regexp_like(r_string,'^[0-9]+{3,}[-+]?[A-Z]?[a-z]?$') as reg
,regexp_like(r_string,'.*[A-Za-z]{3,}.*') as has_3_consecutive_letters
,regexp_like(r_string,'.*\\d+.*\\d+.*') as has_2_digits
,regexp_substr(r_string,'(\\d)',1,1) as first_digit
,regexp_substr(r_string,'(\\d)',1,2) as second_digit
,first_digit <> second_digit as digits_1st_not_equal_2nd
,not(regexp_instr(r_string,regexp_substr(r_string,'(\\d)',1,1),1,2)) as first_digit_does_not_appear_again
,has_3_consecutive_letters and has_2_digits and first_digit_does_not_appear_again as test
from table(generator(rowcount => 10))
//where regexp_like(r_string,'.*[A-Za-z]{3,}.*') // has_3_consecutive_letters
// and regexp_like(r_string,'.*\\d+.*\\d+.*') // has_2_digits
// and not(regexp_instr(r_string,regexp_substr(r_string,'(\\d)',1,1),1,2)) // first_digit_does_not_appear_again
;
Assuming the digits need to be contiguous, you can use a javascript UDF to find the number in a string with with the largest number of distinct digits:
create or replace function f(S text)
returns float
language javascript
returns null on null input
as
$$
const m = S.match(/\d+/g)
if (!m) return 0
const lengths = m.map(m=> [...new Set (m.split(''))].length)
const max_length = lengths.reduce((a,b) => Math.max(a,b))
return max_length
$$
;
Combined with WHERE-clause, this does what you want, I believe:
select column1, f(column1) max_length
from t
where max_length>1 and length(column1)>2 and column1 rlike '[\\w\\d-]+';
Yielding:
COLUMN1 | MAX_LENGTH
------------------------+-----------
abc123def567ghi1111_123 | 3
123 | 3
111222 | 2
Assuming this input:
create or replace table t as
select * from values ('abc123def567ghi1111_123'), ('xyz111asdf'), ('123'), ('111222'), ('abc 111111111 abc'), ('12'), ('asdf'), ('123 456'), (null);
The function is even simpler if the digits don't have to be contiguous (i.e. count the distinct digits in a string). Then core logic changes to:
const m = S.match(/\d/g)
if (!m) return 0
const length = [...new Set (m)].length
return length
Hope that's helpful!
Can someone please explain below behavior
KAP.ADMIN(ADMIN)=> create table char1 ( a char(64000),b char(1516));
CREATE TABLE
KAP.ADMIN(ADMIN)=> create table char2 ( a char(64000),b char(1517));
ERROR: 65536 : Record size limit exceeded
KAP.ADMIN(ADMIN)=> insert into char1 select * from char1;
ERROR: 65540 : Record size limit exceeded => why this error during
insert if create table does not throw any error for same table as
shown above.
KAP.ADMIN(ADMIN)=> \d char1
Table "CHAR1"
Attribute | Type | Modifier | Default Value
-----------+------------------+----------+---------------
A | CHARACTER(64000) | |
B | CHARACTER(1516) | |
Distributed on hash: "A"
./nz_ddl_table KAP char1
Creating table: "CHAR1"
CREATE TABLE CHAR1
(
A character(64000),
B character(1516)
)
DISTRIBUTE ON (A)
;
/*
Number of columns 2
(Variable) Data Size 4 - 65520
Row Overhead 28
====================== =============
Total Row Size (bytes) 32 - 65548
*/
I would like to know the calculation of row size in above case.
I checked the netezza db user guide, but not able to understand its calculation in above example.
I think this link does a good job of explaining the over head of Netezza / PDA Datatypes:
For every row of every table, there is a 24-byte fixed overhead of the rowid, createxid, and deletexid. If you have any nullable columns, a null vector is required and it is N/8 bytes where N is the number of columns in the record.
The system rounds up the size of
this header to a multiple of 4 bytes.
In addition, the system adds a record header of 4 bytes if any of the following is true:
Column of type VARCHAR
Column of type CHAR where the length is greater than 16 (stored internally as VARCHAR)
Column of type NCHAR
Column of type NVARCHAR
Using UTF-8 encoding, each Unicode code point can require 1 - 4 bytes of storage. A 10-character string requires 10 bytes of storage if it is ASCII and up to 20 bytes if it is Latin, or as many as 40 bytes if it is Kanji.
The only time a record does not contain a header is if all the columns are defined as NOT NULL, there are no character data types larger than 16 bytes, and no variable character data types.
https://www.ibm.com/support/knowledgecenter/SSULQD_7.2.1/com.ibm.nz.dbu.doc/c_dbuser_data_types_calculate_row_size.html
First create a temp table based on one row of data.
create temp table tmptable as
select *
from Table
limit 1
Then check the used bytes of the temp table. That should be the size per row.
select used_bytes
from _v_sys_object_storage_size a inner join
_v_table b
on a.tblid = b.objid
and b.tablename = 'tmptable'
Netezza has some Limitations:
1)Maximum number of characters in a char/varchar field: 64,000
2)Maximum row size: 65,535 bytes
Beyond 65 k bytes is impossible for a record length in NZ.
Though NZ box offers huge space, it would be really good idea to move with accurate space forecasting rather radomly spacing. Now in your requirement does all the attributes would mandatorily require a char(64000) or can be compacted with real-time data analysis. If further compacting can be done, then revisit on the attribute length .
Also during such requirements, never go with insert into char1 select * ....... statements because this will allow system to choose preferred datatypes and that will be of higher sizing ends which might not be necessary.
I have read that SQL Server has the ability to create an unsigned integer column and I also read that SQL Server does not allow creation of integer unsigned column. So I'm confused as to which is actually correct.
I need to create a new column in my table called QuantityonHand. This column should be an integer of 5 characters and only accept positive numbers.
So do I create the column as;
(1) QuantityonHand [unsigned] int (5) which means the number can only be positive OR
(2) QuantityonHand int (5) default 0 - which means the number cannot be less than zero, the default 0 being the condition in the column.
I am leaning towards the second one, but I was hoping to get some guidance before I add the column and mess up my table.
Thanks everyone
Josie
There are no unsigned data types, but you can use a check constraint to allow only certain range of values. You can find information for example from here.
First of all there is no UNSIGNED version of INT see: UNSIGNED INTEGER Data Type
I need to create a new column in my table called QuantityonHand. This
column should be an integer of 5 characters and only accept positive
numbers.
Use standard INT and add CHECK constraint.
QuantityonHand INT CHECK (QuantityonHand >= 0 AND QuantityonHand <= 99999)
LiveDemo
The documentation isn't super clear: https://msdn.microsoft.com/en-us/library/ms186939.aspx
What happens if I try to store a 20 character length string in a column defined as nvarchar(10)? Is 10 the max length the field could be or is it the expected length? If I can exceed n characters in the string, what are the performance implications of doing that?
The maximum number of characters you can store in a column or variable typed as nvarchar(n) is n. If you try to store more your string will be truncated, or in case of an insert into a table, the insert would be disallowed with a warning about possible truncation:
String or binary data would be truncated. The statement has been
terminated.
declare #n nvarchar(10)
set #n = N'more than ten chars'
select #n
Result:
----------
more than
(1 row(s) affected)
From my understanding, nvarchar will only only store the provided characters up to the amount defined. Nchar will actually fill in the unused characters with whitespace.
I am trying to prove a table design flaw in a production db, that a table must not have a clustered primary key on a column that can have a random data, in this case a code keyed in by end user.
Though we know the solution is to make the PK as non-clustered, I still need to add rows to it for testing purpose on its replica. Therefore, I will need to know what would be the character I can use after 'Z' as a prefix.
More, the column is not a unicode, and it would be a mess to prefix my fake data with a series of Zs. The table is now having hundred-thousands rows, and each insertion is taking seconds.
Just run this and go down the list. I added the sandwiching dots for clarity, esp. when non-visible characters are involved.
select number, '.' + char(number) + '.' collate SQL_Latin1_General_CP1_CI_AS thechar
from master..spt_values
where type='p' and number between 28 and 255
order by thechar
There are only 4 characters coming after 'Z', since you say the column is not N(Var)Char.
121 .y.
89 .Y.
253 .ý.
221 .Ý.
255 .ÿ.
90 .Z.
122 .z.
208 .Ð.
240 .ð.
254 .þ.
222 .Þ.