How to select a substring till Nth space based on fixed character in SQL Server and Oracle SQL - sql

Question

I need to select a substring based on fixed character length till Nth space. Let me explain the problem.
Let's assume I have three different strings:
Lorem ipsum dolor sit amet, consectetur adipiscing elit
Lorem ipsumdolor sit amet, consectetur adipiscing elit
Lorem ipsum dolorsitamet, consectetur adipiscing elit
If I select 20 character from the beginning of the string I get the following substring sequentially
Lorem ipsum dolor si
Lorem ipsumdolor sit
Lorem ipsum dolorsit
But I want my substring (which is at most 20 characters long) like this
Lorem ipsum dolor
Lorem ipsumdolor sit
Lorem ipsum
That is, I do not want any partial word between two whitespaces
Please help me to generate the query.

Answer 1

Oracle:
select substr(substr(MyField,1,20), 1, instr(substr(MyField,1,20), ' ',-1,1))
from MyTable
SQL Server
SELECT LEFT(MyField, 20 - CHARINDEX (' ' ,REVERSE(LEFT(MyField,20))))
FROM MyTable

Answer 2

For Oracle (it should be possible to translate this to SQL Server, but I don't know SQL Server:
If the first "token" (before the first space) is more than 20 characters, then this will return NULL
if the 21st character is a space, return the first 20 characters
if the 21st character is not a space, but there is a space among the first 20 characters, then chop off the first 20 characters, and then find the "last" space and delete it and everything after it.
If the whole string is at most 20 characters, it should be returned as is.
In the test data below I added two more examples to test if this is working as needed.
with
inputs ( str ) as (
select 'Lorem ipsum dolor sit amet, consectetur adipiscing elit' from dual union all
select 'Lorem ipsumdolor sit amet, consectetur adipiscing elit' from dual union all
select 'Loremipsumdolorsitametconsedtetur' from dual union all
select 'Lorem ipsumdolorsit amet, consectetur etc.' from dual union all
select 'Lorem ipsum dolorsitamet, consectetur adipiscing elit' from dual union all
select 'abcdef ghijk lmno' from dual
),
prep ( str, flag, fragment ) as (
select str,
case when length(str) <= 20 or substr(str, 21, 1) = ' ' then 1 end,
substr(str, 1, 20)
from inputs
)
select str,
case flag when 1 then fragment
else substr(fragment, 1, instr(fragment, ' ', -1) - 1) end
as new_str
from prep;
STR NEW_STR
------------------------------------------------------- --------------------
Lorem ipsum dolor sit amet, consectetur adipiscing elit Lorem ipsum dolor
Lorem ipsumdolor sit amet, consectetur adipiscing elit Lorem ipsumdolor sit
Loremipsumdolorsitametconsedtetur
Lorem ipsumdolorsit amet, consectetur etc. Lorem ipsumdolorsit
Lorem ipsum dolorsitamet, consectetur adipiscing elit Lorem ipsum
abcdef ghijk lmno abcdef ghijk lmno

Answer 3

If SQL Server and if you don't mind a UDF.
Declare #YourTable table (SomeText varchar(500))
Insert Into #YourTable values
('Lorem ipsum dolor sit amet, consectetur adipiscing elit.'),
('Lorem ipsumdolor sit amet, consectetur adipiscing elit'),
('Lorem ipsum dolorsitamet, consectetur adipiscing elit')
Declare #MaxLen int = 20
Select *,Trimmed = [dbo].[udf-Str-TrimToWord](SomeText,#MaxLen)
From #YourTable
Returns
SomeText Trimmed
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Lorem ipsum dolor
Lorem ipsumdolor sit amet, consectetur adipiscing elit Lorem ipsumdolor
Lorem ipsum dolorsitamet, consectetur adipiscing elit Lorem ipsum
The UDF
CREATE FUNCTION [dbo].[udf-Str-TrimToWord] (#String varchar(max),#MaxLen int)
Returns varchar(max)
AS
Begin
Return LEFT(#String,#MaxLen-CharIndex(' ' ,Reverse(Left(#String,#MaxLen))))
End