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Does anybody know which is the SQL command to create relations between tables?

April 26, 2017Command create sql tables

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Does anybody know which is the SQL command to create relations between tables?

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/* create 2 tables named PARENT and CHILD */ CREATE TABLE parent( pfield1 int, pfileld2 char (30) ); CREATE TABLE child ( cfield1 int, cfied2 char(20), cfield3 int ); /* create the primary key for PARENT and CHILD, this field will represent a unique identifier for each of the table */ ALTER TABLE parent add (primary key(pfield1)); ALTER TABLE child add (primary key(cfield1)); /* create the relation between PARENT and CHILD */ ALTER TABLE child ADD ( FOREIGN KEY (cfield3) REFERENCES parent(pfield1)); /* Insert data into parent and child tables */ INSERT INTO parent values(1,’first row’); INSERT INTO parent values(2,’2nd row’); INSERT INTO parent values(3,’tird row’); INSERT INTO child values(1,’first child’,2); INSERT INTO child values(2,’2nd child’,2); INSERT INTO child values(3,’third child’,1); INSERT INTO child values(4,’4th child’,1); /* make a query using relations */ SELECT * FROM parent,child where parent.pfield1=child.cfield3 Good luck in you lesson !