Sql query regarding foreign key dependency
I have two tables, Table A and Table B. Both the table have the "Id" column. Table B is dependent (foreign key) on this "Id". So i want to retrieve the rows which are not present in B.
You seems want :
select a.* from tablea a where not exists (select 1 from tableb b where b.id = a.id);
List Dependencies for SQL Server Foreign Keys, Foreign keys will always have names. The names are called foreign key constraints. You can designate the name for a foreign key constraint in a CREATE TABLE statement or ALTER TABLE statement with the CONSTRAINT keyword. SQL FOREIGN KEY Constraint. A FOREIGN KEY is a key used to link two tables together. A FOREIGN KEY is a field (or collection of fields) in one table that refers to the PRIMARY KEY in another table. The table containing the foreign key is called the child table, and the table containing the candidate key is called the referenced or parent table.
This should work in all flavours of SQL:
select t1.* from TableA t1 left join TableB t2 on t1.id = t2.id where t2.id is null
SQL Server Foreign Key Hierarchy Order and Dependency List Script, The INSERT statement conflicted with the FOREIGN KEY constraint by showing the ordering of objects based on foreign key constraints. Sometimes you must partially copy SQL Server objects from a source to another destination, and if you don't know the object dependency for foreign keys, you can end with some errors of this type: Msg 547, Level 16, State 0, Line 6
CREATE TABLE TableA ( ID INT, [Name] Varchar(500) ) Insert INTO TableA Values(1, 'James') Insert INTO TableA Values(2, 'John') Insert INTO TableA Values(3, 'Betty') Insert INTO TableA Values(4, 'Sherlin')
CREATE TABLE TableB ( TableBID INT, ID INT, Project Varchar(250) ) Insert INTO TableB Values(1, 1, 'ABC') Insert INTO TableB Values(2, 1, 'XYZ') Insert INTO TableB Values(3, 2 , 'ASD') Insert INTO TableB Values(4, 1, 'VGF') Insert INTO TableB Values(5, 3, 'ABC') Insert INTO TableB Values(6, 3, 'XYZ') Insert INTO TableB Values(7, 2, 'FGH')
SELECT * FROM TableA a WHERE exists (SELECT 1 FROM TableB b WHERE b.id = a.id); OR
SELECT * FROM TABLEA a WHERE ID IN (SELECT ID FROM TableB);
DROP TABLE TABLEA DROP TABLE TABLEB
Commonly used SQL Server Constraints: FOREIGN KEY, CHECK , But if we try to create the FOREIGN KEY constraint again on the ID column of the child table, using following ALTER TABLE T-SQL statement: Above query creates following objects and their dependency as shown in following. Find Object Dependencies In SQL Server Management Studio (SSMS) 1. Navigate to Object Explorer in SSMS or Use the F8 keyboard shortcut to open Object Explorer. 2. Expand the database name tree, and navigate to the object name. 3.
SQL Foreign key, This article gives different ways to create a SQL foreign key, rules on is constraint that enforces referential integrity in SQL server database. -1: This query misses foreign keys that are backed by a unique constraint or unique index, rather than by a primary key, in the referenced table. Per MSDN : “A foreign key constraint does not have to be linked only to a primary key constraint in another table; it can also be defined to reference the columns of a UNIQUE constraint in another table.”
SQL FOREIGN KEY Constraint, To create a FOREIGN KEY constraint on the "PersonID" column when the "Orders" table is already created, use the following SQL: MySQL / SQL Server / Oracle Right-click the constraint and then click Delete. In the Delete Object dialog box, click OK. Using Transact-SQL. To delete a foreign key constraint. In Object Explorer, connect to an instance of Database Engine. On the Standard bar, click New Query. Copy and paste the following example into the query window and click Execute.
15. Working with foreign keys, Once you have retrieved data from a table that has foreign key relations to other tables When the cursor is located behind the ON keyword and you select SQL If no foreign key constraint is found linking the "current" and the "previous" table Data Modeler’s diagram only shows the ‘relations’ in a Logical diagram or the foreign keys in a relational model – not any dependencies. So you won’t see lines drawn from tables to their associated DML triggers. But. I do have SOME good news for our questioner – and maybe you, the reader. We can show more. Base Tables from View Query