How to convert C# LINQ query to SQL: explanation and join possibility

Data and Databases
1

Hey everyone! I’m trying to understand a C# LINQ query and figure out how to write it in SQL. Here’s the C# code I’m looking at:

var result = db.Providers
    .Where(n => n.LastName.StartsWith(prefixText))
    .OrderBy(n => n.LastName)
    .Select(n => n.LastName)
    .Take(count)
    .ToArray();

Can someone break this down for me in simple terms? I’m curious about what each part does and how it would look in SQL. Also, I was wondering if it’s possible to add a join to this query somehow. Any help or explanations would be super appreciated! Thanks in advance for your time and knowledge!

2

ooh, interesting query! have u thought about performance? what if u need more provider info? maybe we could tweak it like:

SELECT TOP (count) p.LastName, p.FirstName, d.Department
FROM Providers p
JOIN Departments d ON p.DepartmentId = d.Id
WHERE p.LastName LIKE 'prefixText%'
ORDER BY p.LastName

this joins providers with departments. what do u think?

3

hey jumpingBear! that LINQ query is filtering providers by last name, sorting em, grabbing just the last names, and limiting results. in SQL, it’d be like:

SELECT TOP (count) LastName
FROM Providers
WHERE LastName LIKE ‘prefixText%’
ORDER BY LastName

for joins, you could easily add one before the WHERE clause if ya need data from another table. hope this helps!

4

The LINQ query you’ve presented is indeed quite common in C# applications. To convert it to SQL, you’d essentially be creating a SELECT statement with filtering, ordering, and limiting clauses. Here’s a breakdown:

  1. FROM Providers: This is your base table.
  2. WHERE LastName LIKE ‘prefixText%’: Filters for last names starting with the prefix.
  3. ORDER BY LastName: Sorts the results alphabetically by last name.
  4. SELECT TOP (count) LastName: Selects only the last name column and limits the number of results.

As for adding a join, it’s certainly possible. You could join with related tables like Specialties or Locations if you need additional provider information. The join would typically be placed after the FROM clause but before the WHERE clause in your SQL statement.