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14 paź 2008 · select concat(table_name, '.', column_name) as 'foreign key', concat(referenced_table_name, '.', referenced_column_name) as 'references', constraint_name as 'constraint name' from information_schema.key_column_usage where referenced_table_name is not null;
The essential syntax for a defining a foreign key constraint in a CREATE TABLE or ALTER TABLE statement includes the following: [CONSTRAINT [symbol]] FOREIGN KEY. [index_name] (col_name, ...) REFERENCES tbl_name (col_name,...) [ON DELETE reference_option] [ON UPDATE reference_option] reference_option:
Oracle foreign key constraint syntax. Oracle allows you to create, add, drop, disable, and enable a foreign key constraint. Create a foreign key constraint. The following statement illustrates the syntax of creating a foreign key constraint when you create a table: CREATE TABLE child_table ( ... CONSTRAINT fk_name FOREIGN KEY (col1, col2,...)
The FOREIGN KEY constraint is used to prevent actions that would destroy links between tables. A FOREIGN KEY is a field (or collection of fields) in one table, that refers to the PRIMARY KEY in another table.
The FOREIGN KEY constraint 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 following SQL creates a FOREIGN KEY on the "PersonID" column when the "Orders" table is created:
The essential syntax for a defining a foreign key constraint in a CREATE TABLE or ALTER TABLE statement includes the following: [CONSTRAINT [symbol]] FOREIGN KEY. [index_name] (col_name, ...) REFERENCES tbl_name (col_name,...) [ON DELETE reference_option] [ON UPDATE reference_option] reference_option:
MySQL supports foreign keys, which permit cross-referencing related data across tables, and foreign key constraints, which help keep the related data consistent. A foreign key relationship involves a parent table that holds the initial column values, and a child table with column values that reference the parent column values.
