Convert static SQL to dynamic - sql

Question

I have a static SQL query which finds out blank counts and data types (whether numeric or alphanumeric etc). Below is the query:
SELECT
case when Pattern = '' then 'BLANK' else Pattern end AS Pattern,
LEN(case when Pattern = '' then 'BLANK' else Pattern end) Length,
COUNT(*) AS Count FROM
( SELECT REPLACE(REPLACE( REPLACE( REPLACE( REPLACE(REPLACE( REPLACE( REPLACE( REPLACE(
REPLACE( REPLACE( REPLACE( REPLACE(REPLACE( REPLACE( REPLACE( REPLACE(REPLACE( REPLACE(
REPLACE( REPLACE(REPLACE( REPLACE(
REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE
(REPLACE(REPLACE(REPLACE(REPLACE(UPPER(col_name),'A','A'),'B','A') ,'C','A') ,'D','A')
,'E','A'),'F','A') ,'G','A') ,'H','A') ,'I','A'),'J','A') ,'K','A') ,'L','A') ,'M','A')
,'N','A') ,'O','A') ,'P','A')
,'Q','A'),'R','A') ,'S','A') ,'T','A') ,'U','A') ,'V','A') ,'W','A') ,'X','A') ,'Y','A')
,'Z','A'),'8','N'),'7','N'),'6','N'),'5','N'),'4','N'),'3','N')
,'2','N'),'1','N'),'0','N'),'9','N')
AS Pattern FROM table_name) A GROUP BY Pattern;
How to convert this to a dynamic SQL so that I can iterate over all columns of a table?
Edit
Lets say I have a below table
CREATE TABLE Data (
Column1 varchar(50),
Column2 varchar(50),
Column3 varchar(50),
Column4 varchar(50),
)
INSERT INTO Data
(Column1, Column2, Column3, Column4)
VALUES
(NULL, NULL, 'ABC123', 'abc '),
('xyz', NULL, 'MNO300', 'XYZ123 ')
Now I want a output like below:
Count_Pat_1 --> Count is of only one data type i.e. either Alphabetic or
Numeric
Count_Part_2 --> Count is of mixed data type i.e. contains both alphabet and
number
Col_name Count_Pat_1 Count_Pat_2 Blank
Column1 1 0 1
Column2 0 0 2
Column3 0 2 0
Column4 1 1 0
How can I generate the above table? Clearly I need to resort to Dynamic SQL where the entire sql string needs to be set as variable.
DECLARE #sql nvarchar(max)
SET #sql = N''
SELECT #sql = #sql + CASE WHEN #stm = N'' THEN N'' ELSE N',' END +
'('+
'''' + c.name + ''', '+
'CASE '+
'WHEN ' + QUOTENAME(c.name) + ' IS NULL THEN 1 ' +
'ELSE 0 ' +
'END, ' +
'CASE '+
'WHEN ' + QUOTENAME(c.name) + ' IS NOT NULL THEN LEN(' +
QUOTENAME(c.name) + ') - ** the above SQL script ***
FROM sys.columns c
JOIN sys.tables t ON c.object_id = t.object_id
WHERE t.name = 'Data'
But inserting the above SQL script at the place as indicated by ** will not be giving the output properly.
Hence any hints would be appreciated.
SQL Server version: 2016

Answer 1

With dynamic SQL the trick is to get it working as static SQL first and then convert it to dynamic SQL. Some notes:
To get multiple rows, 1 for each column consider using union all.
To get a count of a case you'll need to use sum.
I've used some possible logic to get a count of one data type or mixed data type but you may find you need more precise logic.
DECLARE #Sql NVARCHAR(MAX) = '';
SELECT #Sql = #Sql
+ CASE WHEN #Sql = '' THEN 'SELECT ' ELSE ' UNION ALL SELECT ' END
+ '''' + c.[name] + ''' ColumnName'
+ ', SUM(CASE WHEN ' + QUOTENAME(c.[name]) + ' IS NOT NULL AND ' + QUOTENAME(c.[name]) + ' NOT LIKE ''%[^0-9.]%'' OR ' + QUOTENAME(c.[name]) + ' NOT LIKE ''%[0-9.]%'' THEN 1 ELSE 0 END) [Count_Pat_1]'
+ ', SUM(CASE WHEN ' + QUOTENAME(c.[name]) + ' IS NOT NULL AND ' + QUOTENAME(c.[name]) + ' LIKE ''%[^0-9.]%'' AND ' + QUOTENAME(c.[name]) + ' LIKE ''%[0-9.]%'' THEN 1 ELSE 0 END) [Count_Pat_2]'
+ ', SUM(CASE WHEN ' + QUOTENAME(c.[name]) + ' IS NULL THEN 1 ELSE 0 END) [Blank]'
+ ' FROM Data'
FROM sys.columns c
JOIN sys.tables t ON c.object_id = t.object_id
WHERE t.[name] = 'Data';
-- print #Sql; -- For debugging
exec sp_executesql #Sql;
Returns as requested:
ColumnName | Count_Pat_1 | Count_Pat_2 | Blank
---------------------------------------------------
Column1 | 1 | 0 | 1
Column2 | 0 | 0 | 2
Column3 | 0 | 2 | 0
Column4 | 1 | 1 | 0