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how to insert data into 2 tables by using one sql query?

Here's how you can structure your SQL queries to insert data into two tables, depending on whether they are related or not:

1. Inserting Data into Two Tables Without a Relationship

If the two tables do not have a relationship, you can simply execute two separate INSERT statements within a single transaction to ensure atomicity:

BEGIN TRANSACTION

-- Insert data into the first table
INSERT INTO FirstTable (Column1, Column2, ...)
VALUES (Value1, Value2, ...)

-- Insert data into the second table
INSERT INTO SecondTable (ColumnA, ColumnB, ...)
VALUES (ValueA, ValueB, ...)

COMMIT TRANSACTION

2. Inserting Data into Two Related Tables

If there is a relationship (e.g., foreign key) between the two tables, you typically need to insert data into the primary (parent) table first and then use the generated key (e.g., ID) to insert data into the related (child) table.

Using a Stored Procedure:

You can utilize a stored procedure to handle this more efficiently:

CREATE PROCEDURE InsertDataIntoRelatedTables
    @Column1 VARCHAR(50),
    @Column2 VARCHAR(50),
    @ColumnA VARCHAR(50),
    @ColumnB VARCHAR(50)
AS
BEGIN
    BEGIN TRANSACTION

    DECLARE @PrimaryKeyID INT

    -- Insert data into the primary (parent) table
    INSERT INTO PrimaryTable (Column1, Column2, ...)
    VALUES (@Column1, @Column2, ...)

    -- Retrieve the generated primary key
    SET @PrimaryKeyID = SCOPE_IDENTITY()

    -- Insert data into the related (child) table
    INSERT INTO RelatedTable (ForeignKeyColumn, ColumnA, ColumnB, ...)
    VALUES (@PrimaryKeyID, @ColumnA, @ColumnB, ...)

    COMMIT TRANSACTION
END

3. Example with Table Variables

Your example using table variables can be structured to reflect the relationship between objects, links, and data. Here’s how you can modify it:

DECLARE @Object_Table TABLE
(
    Id INT NOT NULL PRIMARY KEY
)

DECLARE @Link_Table TABLE
(
    ObjectId INT NOT NULL,
    DataId INT NOT NULL
)

DECLARE @Data_Table TABLE
(
    Id INT NOT NULL IDENTITY(1,1),
    Data VARCHAR(50) NOT NULL
)

-- Insert objects
INSERT INTO @Object_Table (Id) VALUES (1)
INSERT INTO @Object_Table (Id) VALUES (2)

-- Insert data
INSERT INTO @Data_Table (Data) VALUES ('Data One')
INSERT INTO @Data_Table (Data) VALUES ('Data Two')

-- Link all data to the first object
INSERT INTO @Link_Table (ObjectId, DataId)
SELECT Objects.Id, Data.Id
FROM @Object_Table AS Objects, @Data_Table AS Data
WHERE Objects.Id = 1

-- Insert new data and link it to the second object
INSERT INTO @Data_Table (Data)
OUTPUT 2, INSERTED.Id INTO @Link_Table (ObjectId, DataId)
VALUES ('Data Three')

Explanation:

  • Without a Relationship: Two separate INSERT statements are executed. A transaction is used to ensure both inserts succeed or fail together.
  • With a Relationship:
    • Data is first inserted into the parent table.
    • The SCOPE_IDENTITY() function retrieves the ID of the newly inserted row.
    • This ID is then used to insert related data into the child table.
  • Table Variables: In your example, table variables are used to simulate this scenario. Data is inserted into @Object_Table and @Data_Table, and then linked in @Link_Table.

This approach ensures that the data integrity is maintained while inserting related data across multiple tables.

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