Insert data into 2 related tables at once? - sql

Question

I am trying to insert into two tables at once using the primary key from the first table to insert into the second but I am not sure how to go about it.
My table structure is as follows:
Person
PersonId
FirstName
Surname
Employee
EmployeeId
HoursWorked
PersonId in the Person table is an auto incremented column. EmployeeId in the second table is a primary and foreign key that should be the same as PersonId.
I been trying with this query string which I found on Google but with not much luck:
string queryString = "BEGIN TRANSACTION DECLARE #DataID int; "
+"INSERT INTO Person(FirstName, Surname) VALUES(#firstName, #surname);"
+ "SELECT #DataID = scope_identity();"
+ "INSERT INTO Employee VALUES(#DataId, #hoursWorked);"
+ "COMMIT";

Answer 1

From C#, you can try something like this:
// define the INSERT query - insert a firstname,surname into "Person",
// and insert a row into the Emplyoee table with the new ID
// created by the first insert
string insertStmt = #"BEGIN TRANSACTION
INSERT INTO dbo.Person(FirstName, Surname) VALUES(#FirstName, #Surname);
DECLARE #NewPersonId INT = SCOPE_IDENTITY();
INSERT INTO dbo.Employee(EmployeeId, HoursWorked) VALUES(#NewPersonId, #HoursWorked);
COMMIT TRANSACTION;"
// define connection and command for inserting data
using (SqlConnection conn = new SqlConnection(-your-connection-string-here-))
using (SqlCommand cmdInsert = new SqlCommand(insertStmt, conn))
{
// Define parameters - adapt datatype and max length as required
cmdInsert.Parameters.Add("#FirstName", SqlDbType.VarChar, 100);
cmdInsert.Parameters.Add("#Surname", SqlDbType.VarChar, 100);
cmdInsert.Parameters.Add("#HoursWorked", SqlDbType.Int);
// set parameter values
cmdInsert.Parameters["#FirstName"].Value = "John";
cmdInsert.Parameters["#Surname"].Value = "Doe";
cmdInsert.Parameters["#HoursWorked"].Value = 35;
// Open connection, execute query, close connection
conn.Open();
int rowsInserted = cmdInsert.ExecuteNonQuery();
conn.Close();
}
Update: as mentioned by #charlieface, you can write this code more concisely IF you're only ever inserting a single row - like this:
// define connection and command for inserting data
using (SqlConnection conn = new SqlConnection(-your-connection-string-here-))
using (SqlCommand cmdInsert = new SqlCommand(insertStmt, conn))
{
// Define and set parameters
cmdInsert.Parameters.Add("#FirstName", SqlDbType.VarChar, 100).Value = "John";
cmdInsert.Parameters.Add("#Surname", SqlDbType.VarChar, 100).Value = "Doe";
cmdInsert.Parameters.Add("#HoursWorked", SqlDbType.Int).Value = 35;
// Open connection, execute query, close connection
conn.Open();
int rowsInserted = cmdInsert.ExecuteNonQuery();
conn.Close();
}

Answer 2

You need to specify the columns you are inserting into.
You should also use SET XACT_ABORT ON if you have an explicit transaction.
Note also the use of a multi-line string.
string queryString = #"
SET XACT_ABORT ON;
BEGIN TRANSACTION;
INSERT INTO Person (FirstName, Surname)
VALUES(#firstName, #surname);
DECLARE #DataID int = scope_identity();
INSERT INTO Employee (EmployeeId, HoursWorked)
VALUES(#DataId, #hoursWorked);
COMMIT;
";