Say I have a string looking like this ",LI,PA,LK";
I want to remove the first char, so it looks like "LI,PA,LK";
In Java my code to handle this, will look like this:
public String returnSubs(String val) {
int index = val.indexOf(",");
String res = val.substring(index+1, val.length());
return res;
}
I want to achieve the exact same thing in SQL, having this query
select patientID, case when liver is not null then 'LI' else '' end
|| case when kidney_r is not null then ',KR' else '' end
|| case when kidney_l is not null then ',KL' else ''end
|| case when heart is not null then ',HE' else '' end
|| case when liver_domino is not null then ',LI-Dom' else '' end
|| case when lung_r is not null then ',LungR' else '' end
|| case when pancreas is not null then ',PA' else '' end
|| case when liver_split is not null then ',Lsplit' else '' end
|| case when lung_l is not null then ',LungL' else '' end
|| case when intestine is not null then ',Intestine' else '' end
into organType
from offers
where patientID > 1
;
Also, the string I get from the query above, could look like LI, PA, KL, (notice the comma is at the end, and not the begining)
I see that I can use the SUBSTRING and/or INSTR of SQL. But I'm not really sure how. I am creating a procedure where this will be handled
Thanks for any help
Oracle has a function trim() that does exactly what you want:
trim(leading ',' from col)
You can use this in either an update or select.
Note: You appear to be storing multiple values in a comma-delimited list. That is a very bad way to model data. You do not want to overload what strings are by storing multiple values. Oracle has many better alternatives -- association tables, nested tables, JSON, and XML come to mind.
You could also use LTRIM here:
SELECT
LTRIM(organTypes, ',') AS col_out
FROM offers;
Some databases, such as MySQL, offer functions like CONCAT_WS which concatenate with a separator while ensuring that no dangling separators are added to the resulting output. Oracle does not have this, but LTRIM should be sufficient here.
even this will work:
substr(',LI,PA,LK',2)
In SQL SERVER:
SUBSTRING(VAL,2,LEN(VAL))
VAL--> COLUMN NAME
2--> IT SKIPS 1ST VALUE
LEN-->LENGTH OF THE COLUMN
Related
I have seen several similar questions but none cover what I need. I need to put another THEN statement after the first one. My column contains int's. When it returns NULL I need it to display a blank space, but when I try the below code, I just get '0'.
CASE
WHEN Column1 IS NULL
THEN ''
ELSE Column1
END
If I try to put a sting after THEN then it tells me that it cannot convert it from int. I need to convert it to varchar and then change its output to a blank space afterwards, such as:
e.g.
CASE
WHEN Column1 IS NULL
THEN CONVERT(varchar(10), Column1)
THEN ''
ELSE Column1
END
Is there a way of doing this?
Thanks
Rob
A case expression returns a single value -- with a given type. If you want a string result, then you need to be sure that all paths in the case return strings:
CASE WHEN Column1 IS NULL
THEN ''
ELSE CAST(Column1 AS VARCHAR(255))
END
This is more simply written using COALESCE():
COALESCE(CAST(Column1 as VARCHAR(255)), '')
You cannot display an integer as a "blank" (other than using a NULL value).
I have a code that goes like this:
SELECT
'"35933-14",' ||
'"' || us_1.gr_UniqueName || '",' ||
'"' || (CASE WHEN us_1.mls0_PrimaryString = '' THEN 'This is empty'
WHEN CAST(Length(us_1.mls0_PrimaryString) AS INT) < 4 THEN ('Less than 4: '|| SUBSTR(us_1.mls0_PrimaryString,1,10000))
ELSE SUBSTR(us_1.mls0_PrimaryString,1,10000) END) || '",' ||
'"",' ||
'"",' ||
'""'
FROM
us_GroupTab us_1
WHERE (us_1.gr_Active = 1)
AND (us_1.gr_PurgeState = 0)
AND (us_1.gr_PartitionNumber = 0)
AND (us_1.gr_UniqueName IN ('US_HARDWARE_1', 'US_HARDWARE_2','GROUP_NULL'));
Basically the problem is that not all empty string is handled, some users are only inputting multiple spaces which the first case statement does not handle. Is there any way to do this, I have tried using TRIM function but it does not work.
Thanks!
An empty string is the same as null in Oracle, and you can't compare anything to null. You need to use is null instead of = null or = ''.
CASE WHEN TRIM(us_1.mls0_PrimaryString) IS null THEN 'This is empty' ...
You also don't need to cast the length check to int. And the maximum length of a varchar2 before 12c is 4000 chars, so there's no point using 10000 in your substr. In fact the first substr isn't going to do anything anyway as you already know the length is less than 4.
If you want to remove new lines and carriage returns before checking - and that is perhaps something you should be doing client-side, unless you want to store those too - then you can either replace them first:
CASE WHEN TRIM(REPLACE(REPLACE(us_1.mls0_PrimaryString, CHR(10)), CHR(13))) IS null
THEN ...
Or more generically remove all whitespace which would catch tabs etc. too:
CASE WHEN REGEXP_REPLACE(us_1.mls0_PrimaryString, '[[:space:]]') IS NULL THEN ...
Or:
CASE WHEN REGEXP_LIKE(us_1.mls0_PrimaryString, '^[[:space:]]*$') THEN ...
Note that don't need a separate trim with regexp_replace.
Best solution would be to validate and filter that kind of input before it even enters the database.
But as that is not the case, a solution that could work:
regexp_matches()
Quite simply, which of the following methods is better in a WHERE clause to retrieve records where the FIELD_NAME is NOT NULL and NOT Empty
WHERE DATALENGTH(FIELD_NAME) > 0
or
WHERE ISNULL(FIELD_NAME, '') <> ''
Update
I have been informed that the first method gives spurious results for some types of fields... Agree?
Firstly,
select *
from table
where column <> ''
will give exactly the same results as
select *
from table
where isnull(column, '') <> ''
because records where the condition is UNKNOWN rather than FALSE will still be filtered out. I would generally go with the first option.
DATALENGTH counts trailing spaces, which a comparison with '' does not. It is up to you whether you want ' ' to compare unequal to ''. If you do, you need DATALENGTH. If you don't, simply compare with ''.
Note that for TEXT/NTEXT types, comparisons are not supported, but DATALENGTH is.
ISNULL is the best approach instead of DATALENGTH.
I would use
WHERE ISNULL(FIELD_NAME, '') <> ''
One issue that might come up is that a record with a space in it would not be returned. Are you looking for records like that?
I'm not sure about unexpected results from DATALENGTH. I would use the ISNULL method so that SQL Server doesn't need to spend time calculating the length of the record being compared. I don't know the performance difference between the two, just a gut feeling.
if your "not empty" condition encompasses spaces then i would use the nullif
select case when nullif(' ', '') is null then 'y' else 'n' end
y
declare #d varchar(50)
set #d = null
select case when nullif(#d, '') is null then 'y' else 'n' end
y
I would use one of the following:
where coalesce(field_name, '') <> ''
or
where field_name <> '' or field_name is not null
or
where field_name <> ''
The first is standard SQL (coalesce() is standard, isnull() is not). The last is not the most obvious, but NULL will fail the comparison and it allows the use of indexes.
RTRIM(LTRIM(ISNULL(FIELD_NAME, ''))) <> '' will handle spaces and NULLS
In my query I need to pick up this up in a CASE statement
''
Is there a way I could pull those? obviously I can't go "''" or ''''
Actually your second guess was close. Once the string is open '' is the correct way to specify a quote. So your string would be ''''''.
Edit:
SELECT CASE when my_field = '''''' then 'yes' else 'no' end from my_table;
Edit 2:
Based on your comment, are you sure that it has the value ''. It sounds like it is a boolean field. In which case it's value is null. Do you mean something like:
SELECT CASE WHEN my_field IS NULL THEN 'yes' ELSE 'no' END FROM my_table;
SELECT ''' '''
Try the above one..
SQL Syntax is still something I am learning. I am getting the error noted below the this snippet of code.
SELECT
CASE WHEN LTRIM(RTRIM(cLehmanNo)) =' ' THEN NULL
WHEN cLehmanNo IS NOT NULL THEN REPLACE ( cLehmanNo,SUBSTRING (cLehmanNo,PATINDEX( '%[^a-zA-Z0-9 '''''']%',cLehmanNo),1), ' ' )
END asLOAN_NUMBER
,CASE WHEN LTRIM(RTRIM(cMERS)) =' ' THEN NULL
WHEN cMERS IS NOT NULL THEN REPLACE ( cMERS,SUBSTRING (cMERS,PATINDEX( '%[^a-zA-Z0-9 '''''']%',cMERS),1), ' ' )
END asMERS_ID
and 100+ more of same.
Msg 8133, Level 16, State 1, Line 1
None of the result expressions in a CASE specification can be NULL.
What am I doing wrong? How do I keep the gist of the statement and not get this crazy error?
This happens when it can't infer the type.
e.g.
SELECT CASE WHEN 1 = 2 THEN NULL ELSE NULL END
But this works
SELECT CASE WHEN 1 = 2 THEN NULL ELSE replace(NULL,'','') END
so I doubt the error is from the code you have shown us (You are using string functions and the following quick test shows that it will assume that to be varchar(8000))
SELECT CASE WHEN 1 = 2 THEN NULL ELSE REPLACE(NULL,'','') END a
INTO t /*Creates column of datatype varchar(8000)*/
You need to convert NULL to a correct type matching the overall values, e.g. CONVERT(VARCHAR(10), NULL), otherwise the server can't deduce which type to make the resulting value.
The error message actually means that all results in one of your case expressions are null. You have an expression like:
case when something then null when something then null end
At least one of the results has to be something other than null. You could circumvent this, but most likely there is a mistake in the query, as a case exression that always returns the same result is pointless.
The error message has been changed to:
At least one of the result expressions
in a CASE specification must be an
expression other than the NULL
constant.
SELECT
CASE WHEN LTRIM(RTRIM(cLehmanNo)) =' ' THEN NULL
WHEN cLehmanNo IS NOT NULL THEN REPLACE ( cLehmanNo,SUBSTRING (cLehmanNo,PATINDEX( '%[^a-zA-Z0-9 '''''']%',cLehmanNo),1), ' ' )
ELSE ''
END asLOAN_NUMBER
,CASE WHEN LTRIM(RTRIM(cMERS)) =' ' THEN NULL
WHEN cMERS IS NOT NULL THEN REPLACE ( cMERS,SUBSTRING (cMERS,PATINDEX( '%[^a-zA-Z0-9 '''''']%',cMERS),1), ' ' )
ELSE ''
END asMERS_ID