In SQL Server, you can use the UPDATE statement with a SELECT statement to update rows in a table based on data from another table or a subset of data from the same table.

Here's the basic syntax for updating a table with data from a SELECT statement in SQL Server:

UPDATE table1

SET column1 = new_value1, column2 = new_value2, ...

FROM table1

JOIN table2 ON join_condition

WHERE where_condition;


In this syntax:

table1 is the name of the table you want to update.
column1, column2, etc. are the columns you want to update in table1.
new_value1, new_value2, etc. are the new values you want to set for the corresponding columns in table1.
table2 is the name of the table or subquery that you want to use to select data to update table1.
join_condition is the join condition that specifies how to join table1 with table2.
where_condition is an optional condition that specifies which rows in table1 to update.

Here's an example that shows how to update the "quantity" column in the "orders" table based on the "quantity" column in the "order_details" table:

UPDATE orders

SET quantity = order_details.quantity

FROM orders

JOIN order_details ON orders.order_id = order_details.order_id;


This query updates the "quantity" column in the "orders" table with the corresponding values from the "quantity" column in the "order_details" table where the "order_id" values match.