SQL Server 2025 fuzzy string matching(preview)

 Fuzzy (approximate) string matching compares two strings Chto determine how similar they are and to measure their differences. It is used to identify strings that may vary due to character corruption, such as spelling mistakes, transposed or missing characters, or the use of abbreviations. This technique relies on algorithms that detect similarity based on character patterns or phonetic likeness, enabling the matching of strings that sound alike or are nearly identical despite minor variations.

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Samitha

SQL Server LAG() Function

 The SQL LAG() function is a window function used to access a column’s value from a previous row within a defined partition and order. Unlike aggregate functions, it does not reduce the number of rows; instead, it returns a corresponding value for each row. By specifying a partition (e.g., by organisation) and an order (e.g., by year), LAG() enables row-by-row comparisons, such as comparing current values with prior-period values

E.g

SELECT 

    Department,

    Employee,

    SalaryMonth,

    Salary,

    LAG(Salary, 1, 0) 

        OVER (PARTITION BY Department ORDER BY SalaryMonth) AS PrevMonthSalary

FROM EmployeeSalary

ORDER BY Department, SalaryMonth

Result

Department	Employee	SalaryMonth	Salary	PrevMonthSalary
IT	John	2024-01	120000	0
IT	John	2024-02	125000	120000
IT	John	2024-03	130000	125000
HR	Mary	2024-01	90000	0
HR	Mary	2024-02	92000	90000
HR	Mary	2024-03	95000	92000