In this section, we are going to understand the working of PostgreSQL Aliasing, and PostgreSQL Table aliasing, which is used to give a temporary name to the table in the particular command.
What is PostgreSQL Alias?
Advantages of PostgreSQL Aliases
The advantages of PostgreSQL aliasing are given below:
A PostgreSQL alias can be defined in two ways:
In this section, we will understand the PostgreSQL table Aliasing and some examples of it.
What is PostgreSQL Table Alias?
The Table aliasing is used to abbreviate our command to make it easier for reading or when we are implementing a Self-Join, it is listing a similar table more than once in the FROM clause.
The table aliasing works as a nickname for expressing the table names, which make the table name more readable and shorter.
It exists momentarily throughout the implementation of the command. The table aliasing is very useful when the table name is not user-friendly in real-time.
Syntax of PostgreSQL Table Alias
The syntax of the PostgreSQL table alias is given below:
In the below syntax, we ignore the AS keyword because it is optional, and the table _name is given to an alias alias_name.
In the above syntaxes, we have the following parameters:
Examples of PostgreSQL Table aliasing
Let see some examples for our better understanding of PostgreSQL Table aliasing.
Generally, we use a join clause to get records from one or more tables, which contains a similar column name.
We will get an error if we use a similar column name, which comes from one or more tables without fully qualifying them.
To omit this error, we need to qualify these columns with the help of below syntax:
The table aliases were used for one or more tables and linked them with the JOIN clause's help. Here, we are using the table aliases for the table names specified in the FROM clause, and the INNER JOIN clauses that make the command more readable.
In the below example, we have a table named Employee, which contains the below data:
This statement will return the records using table aliases:
On executing the above command, we will get the following result:
Let us assume that our database has one more table named department, which has the following data as we can see in the below screenshot:
As we can observe that both the tables contain one similar column emp_fname.
On executing the above command, we will get the following output, which displays the below error: The column 'emp_fname' in one clause is ambiguous if we use it without table aliases.
Therefore, if we want to avoid the above error, we will use table aliases.
In the below command, we will use the PostgreSQL Inner Join clause to combine the Employee and Department table; and perform the Table aliasing on it.
After executing the above command, we will get the following output:
And if we do not want to use aliases concept with a command, then PostgreSQL uses the table name to find the column name, which makes the statement lengthier and less readable, as we can see in the following example
After executing the above statement, we will get the below output:
To make our commands more readable and save some typing time to write a lengthy table name, we can use the table aliasing.
For example, Instead of using the below expression in a command,
We can give the table long_table_name an alias like below:
And it refers to the column_name in the table Long_table_name with the help of the table alias:
Suppose we want to use table aliases in the Self-join clause. And the self-join clause is used to combine a table to itself, which is referencing a similar table several times within a statement.
In the below example, we will display how to reference the Customer table twice in a similar command with the help of the table aliases:
After implementing the above command, we will get the following results:
In the PostgreSQL table Alias section, we have learned the following topics: