Read columns in SQL tables which are the result of another query - sql

Question

I need to check that all primary key columns do have all values in uppercase.
So, I have a first request which returns me the table-field pairs which are part of PK.
SELECT table_name, field_name FROM dico WHERE pkey > 0;
(dico is some table which gives that information. No need to look it up in the SQL Schema…)
And, for all those pairs tx/fx listed from that first query above, I need to look for values which would not be uppercased.
SELECT DISTINCT 't1', 'f1', f1 FROM t1 WHERE f1 <> UPPER(f1) UNION ALL
SELECT DISTINCT 't2', 'f2', f2 FROM t2 WHERE f2 <> UPPER(f2) UNION ALL
...
SELECT DISTINCT 'tn', 'fn', fn FROM tn WHERE fn <> UPPER(fn);
(I'm putting the table name and field name as "strings" in the output, so that I know from where the wrong values are coming.)
As you see, I do have the code for both requests, but I do not know how to combine them (if possible, in a generic way that would work for both SQL Server and Oracle).
Can you give me some idea on how to finish that?

Answer 1

One way that I could think of is to use a statement block that contains a loop.
Unfortunately, the structure of a statement block will be different for every different database system (the one for SQL Server will be different for Oracle).
I wrote an example using SQL Server further below (fiddle link is at: https://dbfiddle.uk/?rdbms=sqlserver_2017&fiddle=85cd786adf32247da1aa73c0341d1b72).
Just in case, the dynamic query gets very long (possibly longer than the limit of varchar, which is 8000 characters), SQL Server has varchar(max) that can hold up to 2GB (https://learn.microsoft.com/en-us/sql/t-sql/data-types/char-and-varchar-transact-sql?view=sql-server-ver15). This can be used for #DynamicQuery, replacing VARCHAR(3000) in the example below (modified/alternative fiddle link, just to show that the data type really exists and can be used, is at: https://dbfiddle.uk/?rdbms=sqlserver_2017&fiddle=7fbb5d130aad35e682d8ce7ffaf09ede).
Please note that the example is not using your exact queries because I do not have access to the exact same data as the one you have (e.g. I cannot test the example using dico table because I do not have access to that table).
However, I made the example so that it uses a similar basic structure of logic from your queries, so that later on it can be customised to suit your exact need/scenario (e.g. by changing the table names and field names to match the ones that you use, as well as by adding the WHERE clause as you need).
In the example, your 1st query will be run immediately and the result will be handled by a cursor.
After that, a loop (using WHILE statement/structure) will loop through the cursor for the result of the 1st query to dynamically build the 2nd query (inserting the table names and the field names from the 1st query).
Note that at this point, the 2nd query is still being built, not being run yet.
Eventually, after the loop has finished, the resulting/compiled 2nd query will be run/executed (using the EXEC command).
-- START of test data creation.
create table TableA
( message varchar(200)
);
insert into TableA([message]) values ('abc');
insert into TableA([message]) values ('def');
create table TableB
( message varchar(200)
);
insert into TableB([message]) values ('ghi');
insert into TableB([message]) values ('jkl');
-- END of test data creation.
-- START of dynamic SQL
declare #TableAndFieldDetails CURSOR
declare #TableName VARCHAR(50)
declare #FieldName VARCHAR(50)
declare #DynamicQuery VARCHAR(3000) = ''
begin
SET #TableAndFieldDetails = CURSOR FOR
-- START of the 1st query
SELECT [INFORMATION_SCHEMA].COLUMNS.TABLE_NAME,
[INFORMATION_SCHEMA].COLUMNS.COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE INFORMATION_SCHEMA.COLUMNS.COLUMN_NAME LIKE '%message%'
-- END of the 1st query
-- START of dynamically building the 2nd query
OPEN #TableAndFieldDetails
FETCH NEXT FROM #TableAndFieldDetails INTO #TableName, #FieldName
WHILE ##FETCH_STATUS = 0
BEGIN
IF #DynamicQuery <> ''
BEGIN
SET #DynamicQuery += ' UNION ALL '
END
-- The one line right below is each individual part/element of the 2nd query
SET #DynamicQuery += 'SELECT ''' + #TableName + ''', ''' + #FieldName + ''', ' + #FieldName + ' FROM ' + #TableName
FETCH NEXT FROM #TableAndFieldDetails INTO #TableName, #FieldName
END
CLOSE #TableAndFieldDetails
DEALLOCATE #TableAndFieldDetails
-- END of dynamically building the 2nd query
EXEC (#DynamicQuery)
end
-- END of dynamic SQL