SQL INSERT INTO SELECT

In the previous section, we learned about how to insert individual values into a table, one row at a time. What if we want to insert multiple rows into a table? In addition to INSERT INTO, we will combine it with the SELECT statement to achieve this goal. If you are thinking whether this means that you are using information from another table, you are correct. The syntax is as follows:

INSERT INTO "table1" ("column1", "column2", ...)
SELECT "column3", "column4", ...
FROM "table2"

Note that this is the simplest form. The entire statement can easily contain WHERE, GROUP BY, and HAVING clauses, as well as table joins and aliases.

Assuming that we have a table that has the following structure,

Table Store_Information

Column Name	Data Type
store_name	char(50)
Sales	float
Date	datetime

Table Sales_Data

Column Name	Data Type
store_name	char(50)
Product_ID	integer
Sales	float
Date	datetime

Table Sales_Data has detailed sales information, while table Store_Information keeps summarized data on sales by store by day. To move data from Sales_Data to Store_Information, we would type in:

INSERT INTO Store_Information (store_name, Sales, Date)
SELECT store_name, sum(Sales), Date
FROM Sales_Information
GROUP BY store_name, date;

Please note that we specified the order of the columns to insert data into in the example above (the first column is store_name, the second column is Sales, and the third column is Date). While this is not absolutely necessary, it is a good practice to follow, as this can ensure that we are always inserting data into the correct column.