SQL UNION Operator The UNION operator is used to combine the result-set of two or more SELECT statements. Notice that each SELECT statement within the UNION must have the same number of columns. The columns must also have similar data types. Also, the...

SQL LEFT JOIN Keyword The LEFT JOIN keyword returns all rows from the left table (table1), with the matching rows in the right table (table2). The result is NULL in the right side when there is no match. SQL LEFT JOIN Syntax SELECT column_name(s) FROM...

SQL RIGHT JOIN The RIGHT JOIN keyword returns all rows from the right table (table2), with the matching rows in the left table (table1). The result is NULL in the left side when there is no match. SQL RIGHT JOIN Syntax SELECT column_name(s) FROM table1...

SQL FULL OUTER JOIN Keyword The FULL OUTER JOIN keyword returns all rows from the left table (table1) and from the right table (table2). The FULL OUTER JOIN keyword combines the result of both LEFT and RIGHT joins. SQL FULL OUTER JOIN Syntax SELECT column_name(s)...

SQL INNER JOIN Keyword The INNER JOIN keyword selects all rows from both tables as long as there is a match between the columns in both tables. SQL INNER JOIN Syntax SELECT column_name(s) FROM table1 INNER JOIN table2 ON table1.column_name=table2.column_name;...

SQL DEFAULT Constraint The DEFAULT constraint is used to insert a default value into a column. The default value will be added to all new records, if no other value is specified. SQL DEFAULT Constraint on CREATE TABLE CREATE TABLE Persons ( P_Id int NOT...

SQL DEFAULT Constraint The DEFAULT constraint is used to insert a default value into a column. The default value will be added to all new records, if no other value is specified. SQL DEFAULT Constraint on CREATE TABLE CREATE TABLE Persons ( P_Id int NOT...

The NOT NULL constraint enforces a column to NOT accept NULL values. The NOT NULL constraint enforces a field to always contain a value. This means that you cannot insert a new record, or update a record without adding a value to this field. The following...

SQL UNIQUE Constraint The UNIQUE constraint uniquely identifies each record in a database table. The UNIQUE and PRIMARY KEY constraints both provide a guarantee for uniqueness for a column or set of columns. A PRIMARY KEY constraint automatically has...

SQL PRIMARY KEY Constraint The PRIMARY KEY constraint uniquely identifies each record in a database table. Primary keys must contain UNIQUE values. A primary key column cannot contain NULL values. Most tables should have a primary key, and each table...