The WHERE clause is used to extract only those records that fulfill a specified criterion.
The WHERE Format :
SELECT FIELD_NAME,FIELD_NAME FROM TABLE_NAME WHERE FIELD_NAME OPERATOR_VALUE;
The WHERE clause is used to extract only those records that fulfill a specified criterion.
The WHERE Format :
SELECT FIELD_NAME,FIELD_NAME FROM TABLE_NAME WHERE FIELD_NAME OPERATOR_VALUE;
The CONSTRAINT creating value-exclusive column (no twins) or in other words in a single column UNIQUE constraints can not be two records with the same content.
The ADD / DROP CONSTRAINT Format :
ALTER TABLE <TABLE_NAME> ADD CONSTRAINT <CONSTRAINT_NAME> UNIQUE <FIELDNAME>;
ALTER TABLE <TABLE_NAME> ADD CONSTRAINT <CONSTRAINT_NAME> PRIMARY KEY <FIELDNAME>;
ALTER TABLE <TABLE_NAME> DROP CONSTRAINT <CONSTRAINT_NAME>;
The SQL JOIN Statement linking two or more tables to get all the information field.
The JOIN Format :
SELECT <A.FIELDNAME>, <B.FIELDNAME>, .... FROM <TABLE_A> A INNER JOIN <TABLE_B> B ON <A.ID_JOIN>=<B.ID_JOIN>;