My. SQL Foreign Key Create, Add, Drop Foreign Keys Tutorial. Summary in this tutorial, you will learn about My. SQL foreign key and how to create, add, and drop foreign key constraints in My. SQL. Introduction to My. SQL foreign key. A foreign key is a field in a table that matches another field of another table. A foreign key places constraints on data in the related tables, which enables My. SQL to maintain referential integrity. Mysql On Duplicate Key Update Where Clause Change' title='Mysql On Duplicate Key Update Where Clause Change' />A relational database management system uses SQL MERGE also called upsert statements to INSERT new records or UPDATE existing records depending on whether condition. Order of Deletion. If the DELETE statement includes an ORDER BY clause, rows are deleted in the order specified by the clause. This is useful primarily in. This tutorial introduces you to MySQL foreign key and shows you step by step how to create, add and drop foreign keys in MySQL. Sphinx is a fulltext search engine, publicly distributed under GPL version 2. Commercial licensing eg. For removing duplicate rows with multiple fields, first cancate them to the new unique key which is specified for the only distinct rows, then use group by command. In this tutorial, you will learn how to use MySQL UPDATE statement to update data in a table. Hi Geoff Using DEFAULT to generate the value wont work on MariaDB 10. I think well have to use triggers. Lets take a look at the following database diagram in the sample database. We have two tables customers and orders. Each customer has zero or more orders and each order belongs to only one customer. The relationship between customers table and orders table is one to many, and it is established by a foreign key in the orders table specified by the customer. Order Of War Patch Crack Serial more. Number field. The customer. Number field in the orders table relates to the customer. Q So, after update affected rows number will be 0 A If no modifications were made to any rows by the INSERT. ON DUPLICATE KEY UPDATE statement, the ROWCOUNT. SELECT can also be used to retrieve rows computed without reference to any table. For example mysql SELECT 1 1 2. Number primary key field in the customers table. The customers table is called parent table or referenced table, and the orders table is known as child table or referencing table. A foreign key can be a column or a set of columns. The columns in the child table often refer to the primary key columns in the parent table. A table may have more than one foreign key, and each foreign key in the child table may refer to a different parent table. A row in the child table must contain values that exist in the parent table e. Number that exists in the customers table. Multiple orders can refer to the same customer therefore, this relationship is called one customer to many orders, or one to many. Sometimes, the child and parent tables are the same. The foreign key refers back to the primary key of the table e. The report. To column is a foreign key that refers to the employee. Number column which is the primary key of the employees table to reflect the reporting structure between employees i. We have a specific tutorial on the self join to help you query data against this kind of table. The report. To foreign key is also known as recursive or self referencing foreign key. Foreign keys enforce referential integrity that helps you maintain the consistency and integrity of the data automatically. For example, you cannot create an order for a non existent customer. In addition, you can set up a cascade on delete action for the customer. Number foreign key so that when you delete a customer in the customers table, all the orders associated with the customer are also deleted. This saves you time and efforts of using multiple DELETE statements or a DELETE JOIN statement. The same as deletion, you can also define a cascade on update action for the customer. Number foreign key to perform the cross table update without using multiple UPDATE statements or an UPDATE JOIN statement. In My. SQL, the Inno. DB storage engine supports foreign keys so that you must create Inno. DB tables in order to use foreign key constraints. Creating foreign keys for tables. My. SQL creating foreign key syntax. The following syntax illustrates how to define a foreign key in a child table in CREATE TABLE statement. CONSTRAINT constraintname. FOREIGN KEY foreignkeyname columns. REFERENCES parenttablecolumns. ON DELETE action. ON UPDATE action. CONSTRAINTconstraintname. FOREIGN KEYforeignkeynamecolumnsREFERENCESparenttablecolumnsLets examine the syntax in greater detail The CONSTRAINT clause allows you to define constraint name for the foreign key constraint. If you omit it, My. SQL will generate a name automatically. The FOREIGN KEY clause specifies the columns in the child table that refers to primary key columns in the parent table. You can put a foreign key name after FOREIGN KEY clause or leave it to let My. SQL create a name for you. Notice that My. SQL automatically creates an index with the foreignkeyname name. The REFERENCES clause specifies the parent table and its columns to which the columns in the child table refer. The number of columns in the child table and parent table specified in the FOREIGN KEY and REFERENCES must be the same. The ON DELETE clause allows you to define what happens to the records in the child table when the records in the parent table are deleted. If you omit the ON DELETE clause and delete a record in the parent table that has records in the child table refer to, My. SQL will reject the deletion. In addition, My. SQL also provides you with actions so that you can have other options such as ON DELETE CASCADE that ask My. SQL to delete records in the child table that refers to a record in the parent table when the record in the parent table is deleted. If you dont want the related records in the child table to be deleted, you use the ON DELETE SET NULL action instead. My. SQL will set the foreign key column values in the child table to NULL when the record in the parent table is deleted, with a condition that the foreign key column in the child table must accept NULL values. Notice that if you use ON DELETE NO ACTION or ON DELETE RESTRICT action, My. SQL will reject the deletion. The ON UPDATE clause enables you to specify what happens to the rows in the child table when rows in the parent table are updated. You can omit the ON UPDATE clause to let My. SQL reject any updates to the rows in the child table when the rows in the parent table are updated. The ON UPDATE CASCADE action allows you to perform a cross table update, and the ON UPDATE SET NULL action resets the values in the rows in the child table to NULL values when the rows in the parent table are updated. The ON UPDATE NO ACTION or UPDATE RESTRICT actions reject any updates. My. SQL creating table foreign key example. The following example creates a dbdemo database and two tables categories and products. Each category has one or more products and each product belongs to only one category. The catid field in the products table is defined as a foreign key with UPDATE ON CASCADE and DELETE ON RESTRICT actions. CREATE DATABASE IF NOT EXISTS dbdemo. CREATE TABLE categories. ENGINEInno. DB. CREATE TABLE products. FOREIGN KEY fkcatcatid. REFERENCES categoriescatid. ON UPDATE CASCADE. ON DELETE RESTRICT. ENGINEInno. DB CREATEDATABASEIF NOT EXISTSdbdemo   catidintnot nullautoincrementprimary key,   catnamevarchar2. FOREIGN KEYfkcatcatid   REFERENCEScategoriescatidAdding a foreign key to a table. My. SQL adding foreign key syntax. To add a foreign key to an existing table, you use the ALTER TABLE statement with the foreign key definition syntax above. ALTER tablename. ADD CONSTRAINT constraintname. FOREIGN KEY foreignkeynamecolumns. REFERENCES parenttablecolumns. ON DELETE action. ON UPDATE action ADDCONSTRAINTconstraintname. FOREIGN KEYforeignkeynamecolumnsREFERENCESparenttablecolumnsMy. SQL adding foreign key example. Now, lets add a new table named vendors and change the products table to include the vendor id field. CREATE TABLE vendors. ENGINEInno. DB. ALTER TABLE products. ADD COLUMN vdrid int not null AFTER catid    vdridintnot nullautoincrementprimary key,ADDCOLUMNvdridintnot null. AFTERcatid To add a foreign key to the products table, you use the following statement. ALTER TABLE products. ADD FOREIGN KEY fkvendorvdrid. REFERENCES vendorsvdrid. ON DELETE NO ACTION. ON UPDATE CASCADE ADDFOREIGN KEYfkvendorvdridREFERENCESvendorsvdridNow, the products table has two foreign keys, one refers to the categories table and another refers to the vendors table. Dropping My. SQL foreign key. You also use the ALTER TABLE statement to drop foreign key as the following statement. ALTER TABLE tablename. DROP FOREIGN KEY constraintname DROPFOREIGN KEYconstraintname In the statement above First, you specify the table name from which you want to remove the foreign key. Second, you put the constraint name after the DROP FOREIGN KEY clause. Notice that constraintname is the name of the constraint specified when you created or added the foreign key to the table. If you omit it, My. SQL generates a constraint name for you. Mysql insert two actions if key isnt duplicated. No. Its not possible to call a stored procedure from an INSERT statement. There is a way to call a stored program from an INSERT statement, but it has to be a user defined function, for example INSERT INTO sometable col. SELECT IF userdefinedfunction, abc, abc. But that function is going to get called whether the resulting row throws a duplicate key exception or not. Its also possible to reference a user defined function within the ON DUPLICATE KEY clause. INSERT INTO sometable col. SELECT IF userdefinedfunction, abc, abc. ON DUPLICATE KEY UPDATE col. IF udfduplicate, VALUEScol. VALUEScol. 1. Note that there are issues with binary logging row vs. So I dont think you really want to go with this approach. If you are inserting a single row, you are probably going to be better off performing the INSERT. ON DUPLICATE KEY UPDATE. An affected rows value of 1 will tell you that a row was inserted, an affected rows value of 2 means the row was updated, so you could conditionally call the procedure you want. If you always want the actions in those stored procedures called whenever any row is inserted or updated, you might consider AFTER INSERT and AFTER UPDATE triggers. You need to test to be sure the AFTER UPDATE trigger gets fired from an ON DUPLICATE KEY UPDATE. My. SQL where an AFTER UPDATE trigger wasnt getting called. EDIT The most recent update to the original question specifies this INSERT statement is performed from within a My. SQL stored procedure. I would recommend this type of approach DECLARE affectedrows INT. INSERT INTO sometable id,foo VALUES 1. ON DUPLICATE KEY UPDATE foo VALUESfoo. SELECT ROWCOUNT INTO affectedrows. IF affectedrows 1 THEN. CALL storedprocedureafterinsert. CALL storedprocedureafterupdate. Q So, after update affected rows number will be 0 A If no modifications were made to any rows by the INSERT. ON DUPLICATE KEY UPDATE statement, the ROWCOUNT function will return 0. If no rows are inserted, and a single row is updated, then the ROWCOUNT function will return a 2. The difference between getting a 0 and an 2 is whether the row is actually modified or not. When the result of the update results in the row being identical to the current contents of the row no changes made, then ROWCOUNT returns a 0. If the update results in a change to the row, the ROWCOUNT will be 2.