case and concatenation, sql - sql

Question

Im using a SQL server database and im having a hard time with my case statement. What I'm trying to do is insert a concatenation of attributes into an id field (state_issue_teacher_id) when it equals '' (empty field). The problem is that I have some empty id fields that I need to fill with a unique id that is created by a concatenation of attributes through the case statement.
The empty rows above I need to fill with a concatenation of last_name+first_name+gender+race_ethnicity_code+high_degree_code+position_code+assignment_code.
Here is what I have so far:
SELECT
state_issue_teacher_id,
region_code
+ county_code
+ district_code AS district_code ,
last_name ,
first_name ,
assigned_fte = CASE assign_fte
WHEN '' THEN 0
ELSE CAST(assign_fte AS NUMERIC(18,
2))
END ,
CASE WHEN state_issue_teacher_id = '' THEN
RTRIM([last_name]) + '_' + RTRIM([first_name]) + '_' + RTRIM([gender])
+ '_' + RTRIM([race_ethnicity_code]) + '_' + high_degree_code + '_'
+ position_code + '_' + assignment_code
ELSE state_issue_teacher_id
END,
year_time
FROM dbo.example

Answer 1

When concatenating like that you need to account for two possible problems.
First are all of the fields you are concatenating together varchar (or nvarchar) or are some of them int or numeric? If your datatypes are not varchar or nvarchar, then you need to convert them to use them in a concatentation.
The next possible problem is if one or more of the values can be null. You will need to coalesce any value that could be null with a varchar value (usually a space or empty string for a concatenations although sometimes the value "unknown" works too)) or the concatenation will return null as null concatenated with anything else is null.

Answer 2

SELECT
state_issue_teacher_id,
region_code
+ county_code
+ district_code AS district_code ,
last_name ,
first_name ,
assigned_fte = CASE assign_fte
WHEN '' THEN 0
ELSE CAST(assign_fte AS NUMERIC(18,
2))
END ,
CASE WHEN state_issue_teacher_id = '' THEN
RTRIM(coalesce([last_name],'ValueYouUseInsteadOfNull')) + '_' +
RTRIM(coalesce([first_name],'ValueYouUseInsteadOfNull')) + '_' +
RTRIM(coalesce([gender],'ValueYouUseInsteadOfNull')) + '_' +
RTRIM(coalesce([race_ethnicity_code],'ValueYouUseInsteadOfNull')) + '_' +
coalesce(high_degree_code,'ValueYouUseInsteadOfNull') + '_' +
coalesce(position_code,'ValueYouUseInsteadOfNull') + '_' +
coalesce(assignment_code,'ValueYouUseInsteadOfNull')
ELSE state_issue_teacher_id
END,
year_time
FROM dbo.example
Odds are, you have null in some of those fields.
Give this query a try.

Answer 3

Thank you for everyone that answered the question. I got it to work with the below query.
SELECT
state_issue_teacher_id,
region_code
+ county_code
+ district_code AS district_code ,
last_name ,
first_name ,
gender,
race_ethnicity_code,
high_degree_code,
position_code,
assignment_code,
assigned_fte = CASE assign_fte
WHEN '' THEN 0
ELSE CAST(assign_fte AS NUMERIC(18,
2))
END ,
state_issue_teacher_id =
CASE state_issue_teacher_id WHEN '' THEN
RTRIM([last_name]) + '_' + RTRIM([first_name]) + '_' + RTRIM([gender])
+ '_' + RTRIM([race_ethnicity_code]) + '_' + high_degree_code + '_'
+ position_code + '_' + assignment_code
ELSE state_issue_teacher_id
END,
year_time
FROM dbo.example

Answer 4

How about?:
update example
set state_issue_teacher_id =
RTRIM([last_name]) + '_' + RTRIM([first_name]) + '_' + RTRIM([gender])
+ '_' + RTRIM([race_ethnicity_code]) + '_' + high_degree_code + '_'
+ position_code + '_' + assignment_code
WHERE isnull(state_issue_teacher_id, '') = ''