Redshift Primary key constraint is informational only; they are not enforced by Amazon Redshift. Amazon data warehouse appliance supports referential integrity constraints such as Redshift primary key, foreign key, and unique keys as part of SQL-92 standard requirement. You can create primary key constraint while creating tables in Redshift database but it will not be enforced while loading Redshift tables. Redshift query planner uses these constraints to create better query execution plan. If Primary key is set at the column level, it must be on a single column. If PRIMARY…

Data type is an attribute that specifies type of data of any object that is going to be stored in that particular column. Each column, variable and expression has related data type in SQL. However, different database offers the different data types for columns. Redshift data types are almost similar to what the traditional RDBMS supports. Amazon Redshift data types are similar to IBM Netezza data types. When you issue Redshift create table command each column in a database tables must have name and a data type associated with it.…

Redshift WITH Clause is an optional clause that always precedes SELECT clause in the query statements. WITH clause has a subquery that is defined as a temporary tables similar to View definition. Each subquery in the WITH clause specifies a table name, an optional list of column names, and a query expression that evaluates to a table (usually a SELECT statement). In SQL, WITH clause are commonly referred to as Common Table Expressions (CTE). A CTE or WITH clause is a syntactical sugar for a subquery. Where you can use…