This SQL query performs the following operations: 1. It uses a...

This SQL query performs the following operations:

1. It uses a LEFT OUTER JOIN to combine data from three tables: [Your Table] (aliased as a), trediumclientcrosswalk (aliased as b), and organizations (aliased as c).

   • A LEFT OUTER JOIN ensures that all rows from the left table (a in the first join, or the result so far in the second join) are included in the output.
   • Any rows in the right table (b for the first join or c for the second join) that do not have a matching value will result in NULL values for those right-table columns.

2. The joins happen in the following steps:

   First Join:

   [Your Table] AS a
   LEFT OUTER JOIN trediumclientcrosswalk b 
   ON a.Group_Id = b.Tredium_group_id
   

   • For every row in the [Your Table] table (a), it attempts to match rows from the trediumclientcrosswalk table (b) where a.Group_Id matches b.Tredium_group_id.
   • If no match is found in b, the result will still include the row from a, but with NULL for the b table's columns.

   Second Join:

   LEFT OUTER JOIN organizations c 
   ON b.ehgroupid = c.organizationcode 
   OR a.group_id = c.organizationcode
   

   • For every row in the result set so far, it joins with the organizations table (c) using two conditions with an OR operator:
     1. b.ehgroupid = c.organizationcode
     2. a.group_id = c.organizationcode
   • If no match is found in c for either condition above, the row will still be included, but columns from the c table will contain NULL values.

Summary:

The code joins three tables using two LEFT OUTER JOIN operations:

• First, it matches rows between [Your Table] (a) and trediumclientcrosswalk (b) based on Group_Id and Tredium_group_id.
• Then it joins the result with the organizations table (c) either on b.ehgroupid = c.organizationcode or a.group_id = c.organizationcode.
• The query ensures all rows from [Your Table] are present in the output, even if no matches exist in the other two tables, resulting in NULL for missing values.