Yesterday I was working on a project that required me to create a SQL query to generate a table of accounts receivables pathways. I thought it would be interesting to share the SQL code I wrote for this task. The code is as follows:

-- Create the table in the specified schema
-- Create a new table called 'c_tableau_collector_pathway_tbl' in schema 'dbo'
-- Drop the table if it already exists
IF OBJECT_ID('dbo.c_tableau_collector_pathway_tbl', 'U') IS NOT NULL
DROP TABLE dbo.c_tableau_collector_pathway_tbl
GO
-- Create the table in the specified schema
CREATE TABLE dbo.c_tableau_collector_pathway_tbl
(
    c_tableau_collector_pathway_tblId INT NOT NULL IDENTITY(1, 1) PRIMARY KEY, -- primary key column
    pt_no VARCHAR(50) NOT NULL,
    collector_dept_path VARCHAR(MAX)
);

WITH tmp AS (
    SELECT DISTINCT pt_no
    FROM sms.dbo.c_tableau_times_with_worklist_tbl
    )
INSERT INTO sms.dbo.c_tableau_collector_pathway_tbl (
    pt_no,
    collector_dept_path
    )
SELECT rtrim(ltrim(tmp.pt_no)) AS [pt_no],
    stuff((
            SELECT ', ' + z.collector_dept
            FROM sms.dbo.c_tableau_times_with_worklist_tbl AS z
            WHERE z.pt_no = tmp.pt_no
            GROUP BY z.collector_dept
            ORDER BY max(event_number)
            FOR XML path('')
            ), 1, 2, '') AS [collector_dept_path]
FROM tmp AS tmp;

select pt_no,
    [collector_dept_path],  
    [number_of_distinct_collector_dept] = (LEN(REPLACE(collector_dept_path, ',', '**')) - LEN(collector_dept_path)) + 1
from dbo.c_tableau_collector_pathway_tbl

So what does it do? Let’s break it down step by step:

1. IF OBJECT_ID('dbo.c_tableau_collector_pathway_tbl', 'U') IS NOT NULL
   • This part checks if a table named c_tableau_collector_pathway_tbl exists in the dbo schema. If it does, it proceeds to the next step.
2. DROP TABLE dbo.c_tableau_collector_pathway_tbl
   • If the table exists, it drops (deletes) the table c_tableau_collector_pathway_tbl.
3. CREATE TABLE dbo.c_tableau_collector_pathway_tbl (...)
   • This part creates a new table named c_tableau_collector_pathway_tbl in the dbo schema with three columns:
     • c_tableau_collector_pathway_tblId of type INT, which is the primary key and automatically increments by 1 for each new row.
     • pt_no of type VARCHAR(50), which stores values up to 50 characters long and cannot be NULL.
     • collector_dept_path of type VARCHAR(MAX), which can store large amounts of text.
4. WITH tmp AS (...)
   • This part defines a temporary table (tmp) that contains distinct values of pt_no from another table named sms.dbo.c_tableau_times_with_worklist_tbl.
5. INSERT INTO sms.dbo.c_tableau_collector_pathway_tbl (...) SELECT ...
   • This part inserts data into the newly created c_tableau_collector_pathway_tbl table. It selects distinct pt_no values from the temporary table tmp and concatenates corresponding collector_dept values into a single string, separated by commas. The FOR XML path('') part formats the result as XML, and stuff(..., 1, 2, '') removes the leading comma and space.
6. SELECT pt_no, [collector_dept_path], [number_of_distinct_collector_dept] = (...)
   • Finally, this part selects data from the c_tableau_collector_pathway_tbl table. It selects pt_no, collector_dept_path, and calculates the number of distinct collector departments by counting the commas in the collector_dept_path string.

In summary, this SQL code drops an existing table (if it exists), creates a new table with specific columns, inserts data into the new table by concatenating values from another table, and then selects data from the new table along with a calculated value for the number of distinct collector departments.