How do I UPDATE from a SELECT in SQL Server?

📝 Tech Blog: Updating a Table with SELECT in SQL Server

👋 Hey there fellow tech enthusiasts! Today, we're diving into a commonly asked question in the world of SQL Server: "How do I update a table using SELECT?" 🤔

When it comes to SQL Server, we all know it's possible to insert rows into a table using an INSERT.. SELECT statement. But can we use a SELECT statement to update a table? Let's find out! 💡

🔍 The Scenario: Imagine you have a temporary table with some values, and you want to update another table using those values. Let's say we have a table called Table, and we want to update the col1 and col2 columns based on the values in the other_table table. Our initial attempt might look something like this:

UPDATE Table SET col1, col2
SELECT col1, col2 
FROM other_table 
WHERE sql = 'cool'
WHERE Table.id = other_table.id

🛑 The Problem: But hold your horses! 🐎 Unfortunately, this syntax won't work and will throw a syntax error. Updating a table with values obtained from a SELECT statement requires a slightly different approach.

💡 The Solution: Fortunately, SQL Server provides a handy alternative using the FROM clause in combination with the UPDATE statement.

Here's the correct syntax to update Table using the values from other_table:

UPDATE Table
SET col1 = other_table.col1,
    col2 = other_table.col2
FROM other_table
WHERE Table.id = other_table.id
  AND other_table.sql = 'cool'

✨ Explanation: Let's break down the updated syntax:

1. We use the UPDATE statement to specify the table we want to update, which is Table in our case.

2. Next, we use the SET clause to assign values to the columns we want to update. We assign the values from other_table.col1 to Table.col1, and similarly for col2.

3. The FROM clause comes into play, allowing us to join other_table with Table based on the common id column.

4. Finally, we add a WHERE clause to filter the rows we want to update. In this example, we're updating rows where other_table.sql is equal to 'cool'.

🚀 Time to Shine! With this updated syntax, you can now confidently update a table using values from a SELECT statement in SQL Server. 🎉

So go ahead, test out the code, and start updating your tables like a pro! 💪 And don't hesitate to share your experiences or any questions you may have in the comments below. Let's level up our SQL game together! 😄

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Thanks for reading, and happy SQL updating! 🎊✨