Before I show you the multi-table solution, let me demonstrate the simplest form of the --UPDATE C SET /* SELECT *, -- */ order_count = FROM dbo.
Customers AS C JOIN( SELECT O.customer_id, COUNT(1) cnt FROM dbo.
Any characters not found in this code page are lost.
DEFAULT Specifies that the default value defined for the column is to replace the existing value in the column.
The query is using the UPDATE to iterate over the INNER JOIN.
As such the ON functions as your WHERE clause and the INNER JOIN skips records that are not found in the JOINed table.
Customers AS C JOIN order_counts AS OC ON C.customer_id = OC.customer_id ) UPDATE COC SET /* SELECT *, -- */ order_count = COC.new_order_cnt FROM customer_order_counts AS COC; would happily update each customer multiple times, each time overwriting the prior change. The problem with that is that there is no guarantee in which order that happens.Specifies the condition to be met for the rows to be updated.The search condition can also be the condition upon which a join is based.This can also be used to change the column to NULL if the column has no default and is defined to allow null values.Compound assignment operator: = Add and assign -= Subtract and assign *= Multiply and assign /= Divide and assign %= Modulo and assign &= Bitwise AND and assign ^= Bitwise XOR and assign |= Bitwise OR and assign Returns updated data or expressions based on it as part of the UPDATE operation.