PSLine2000Documentation/Queries/Processes by List.md

Processes by List

Analysis generated on: 4/2/2025 10:05:48 AM

SQL Statement

SELECT Process.*, Metals.Density
FROM ([Process by List] LEFT JOIN Process ON [Process by List].PN = Process.PartNumber) LEFT JOIN Metals ON Process.MetalType = Metals.PartNo
WHERE (((Process.PartNumber)<>""));

Dependencies

• Tables/Process
• Queries/Metals

Parameters

• None

What it does

SQL Code Explanation

Overview

This SQL query retrieves data from two tables, Process and Metals, joining them based on certain conditions. The query uses subqueries to first create a temporary result set containing Process data and then joins it with the Metals table.

Breakdown of the Query

Subquery: [Process by List]

This is an ad-hoc SQL query that creates a temporary result set ([Process by List]) containing data from the Process table. The subquery uses a LEFT JOIN operation to include all rows from both tables.

SELECT Process.*, Metals.Density
FROM ([Process by List] LEFT JOIN Process ON [Process by List].PN = Process.PartNumber)

• The subquery selects all columns (*) from the Process table and joins it with itself (noting that this might be considered redundant and inefficient).
• It then uses a LEFT JOIN to include rows from both tables where the join condition is met.

Main Query

The main query builds upon the subquery, adding another LEFT JOIN operation to incorporate data from the Metals table.

LEFT JOIN Metals ON Process.MetalType = Metals.PartNo

• This join operates on the MetalType column in the Process table and the PartNo column in the Metals table.
• It includes rows from both tables where there is a match in these columns.

Filtering Condition

The query uses an inequality condition to exclude rows with empty strings (\u003c\u003e"").

WHERE (((Process.PartNumber)\u003c\u003e""));

• This ensures that only rows with non-empty PartNumber values are included in the final result set.
• The double parentheses around the comparison operation allow for the use of the NOT operator.

Final Result

The entire query is executed as a single operation, producing the following:

• A temporary result set containing data from both tables after applying the join conditions and filtering out empty strings.
• The final result includes all columns (*) from the Process table, along with the density of metals for each part number.