How Can I Access Previous Row Values in SQL SELECT Statements?

Retrieving Previous Row Data within SQL SELECT Statements

Accessing data from the preceding row directly within a standard SQL SELECT statement isn't typically supported. However, specific functions can help achieve this.

To compute the difference between consecutive rows, SQL Server's LAG function proves invaluable. Here's the syntax:

<code class="language-sql">SELECT value - LAG(value) OVER (ORDER BY Id) AS difference FROM table;</code>

The LAG function retrieves the value from the previous row of the value column, ordered by the Id column. This allows for calculations comparing adjacent rows, effectively providing access to the previous row's data within the SELECT statement.

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