SQL Server is a powerful database management system that offers various techniques for manipulating data. In this article, we will explore an interesting concept called the Temp In-Place method, which was commonly used in the early days of computing.

The Temp In-Place method is a technique that allows you to perform intermediate operations on a table without the need for additional temporary tables or identity columns. It involves using the existing table and manipulating the data by assigning different key values to avoid conflicts with the original records.

Let’s consider a scenario where we have a table called [SOURCE] with three columns: [Name], [Age], and [Sex]. The table contains duplicate rows, and we want to delete the first row from each set of duplicates while preserving the other duplicates. Additionally, any single rows should also be deleted.

In modern SQL Server versions, this problem can be solved using various approaches such as cursors or the GROUP BY clause. However, in the early days of computing, when storage space was limited and adding columns or using temporary tables was a complex process, the Temp In-Place method was a valuable technique.

Let’s dive into an example to understand how the Temp In-Place method works. Consider the following table:

CREATE TABLE SOURCE (
    Name VARCHAR(50),
    Age INT,
    Sex CHAR(1)
);

INSERT INTO SOURCE (Name, Age, Sex)
VALUES
    ('ABC', 24, 'M'),
    ('ABC', 24, 'M'),
    ('LMN', 27, 'M'),
    ('LMN', 27, 'M'),
    ('LMN', 27, 'M'),
    ('PQRS', 25, 'F'),
    ('XYZ', 24, 'M'),
    ('XYZ', 25, 'M');

In this example, we want to delete the first row from each set of duplicates based on the [Name], [Age], and [Sex] columns. To achieve this using the Temp In-Place method, we can follow these steps:

1. Re-map the [Sex] column values to the lowest bit: 0 for ‘M’ and 1 for ‘F’.
2. Create counted rows using the upper 7 bits of the [Sex] column to store the duplicate counts.
3. Remove the original rows.
4. Generate new rows with the correct duplicate counts.
5. Clean up the temporary rows and restore the original [Sex] values.

By following these steps, we can achieve the desired result without the need for additional tables or identity columns.

Although the Temp In-Place method may not be commonly used in modern SQL Server development, understanding these historical techniques can be valuable. It allows us to appreciate the advancements in database management systems and provides alternative solutions when faced with limited resources or unique constraints.

SQL Server offers a wide range of features and techniques that can be utilized to solve various data manipulation challenges. As a SQL Server developer, it’s important to explore different concepts and stay updated with the latest advancements in the field.

Thank you for reading this article on the Temp In-Place method in SQL Server. We hope you found it informative and gained a deeper understanding of database manipulation techniques. Stay tuned for more articles exploring SQL Server concepts and ideas.