Advances in web-based technologies, particularly HTML5, have made online data modeling a more credible option than ever. Tools have emerged that make it easy and efficient to design a database and generate the SQL code for a specific database product, offering a viable alternative to an on-premises solution, at least in certain circumstances. PgAdmin is one of the most popular Open Source administration and development platforms for PostgreSQL. It's designed to meet the needs of both novice and experienced PostgreSQL users alike, providing a powerful graphical interface that simplifies the creation, maintenance and use of database objects.
There are times within Postgres where you may want to generate sample data or some consistent series of records to join in order for reporting. Enter the simple but handy set returning function of Postgres: generate_series. generate_series as the name implies allows you to generate a set of data starting at some point, ending at another point, and optionally set the incrementing value. generate_series works on two datatypes:
- integers
- timestamps
Let's get started with the most basic example:
So generate_series pretty straight-forward, but what interesting ways can it be used?
Generating fake data
By putting our generate_series inside a CTE we can easily now generate a set of numbers and then perform some operation against each value. If we want to generate some fake number we can use random() which generates a random number between 0.0 and 1.0.
Pretty weekly reporting with joins
Aggregating across some time dimension is a fairly common report. A good example might be new users per week. The simplest way to get this would be by leveraging Postgres date_trunc function:
The issue with the above query arises when two cases are true, first you're charting your data over time and then two you have a week with no sign-ups. In the case of no sign-ups in a week you'd simply miss the 0 on your graph leaving a misleading impression. To smooth this out we go back to generate series and do an outer join on the week:
What other uses do you have for generate_series?
Postgres has a wealth of hidden gems within it. generate_series is just one of the handy built-in features of Postgres. If you know of other novel uses for it we'd love to hear about it @citusdata.
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In this section, we are going to understand the working of PostgreSQL Serial pseudo-type, which allows us to define auto-increment columns in tables. And we also see examples of the PostgreSQL Serial pseudo-type.
What is PostgreSQL Serial pseudo-type?
In PostgreSQL, we have one particular kind of database object generator known as Serial, which is used to create a sequence of Integers that are frequently used as a Primary key in a table.
The sequence can be generated with the help of the SERIAL pseudo-type, while we are creating a new table, as we can see in the following command:
The PostgreSQL does the following if we provide the SERIAL pseudo-type to the ID column:
- Firstly, PostgreSQL will create a sequence object and then establish the next value created by the sequence as the particular column's pre-defined value.
- After that, PostgreSQL will enhance a NOT NULL constraint to the ID column since a sequence always produces an integer that is a non-null value.
- At last, PostgreSQL will provide the owner of the sequence to the ID column; as an output, the sequence object is removed when the table or ID column is dropped.
Note: We can use both the command to specify the Serial pseudo-type as both the below command is similar to each other.
The PostgreSQL Serial pseudo-type has been classified into three types which are as follows:
- SMALLSERIAL
- SERIAL
- BIGSERIAL
We have the following table, which contains all the Serial pseudo-type specification that is supported by PostgreSQL:
| Name | Storage Size | Range |
|---|---|---|
| SMALLSERIAL | 2 bytes | 1 to 32767 |
| SERIAL | 4 bytes | 1 to 2147483647 |
| BIGSERIAL | 8 bytes | 1 to 9223372036854775807 |
Syntax of PostgreSQL Serial pseudo-type
The syntax of the PostgreSQL Serial pseudo-type as follows:
Examples of PostgreSQL SERIAL type
Let us see different examples to understand how the PostgreSQL Serial pseudo type works.
Note: We can define the PRIMARY KEY constraint for the SERIAL column because the SERIAL type does not indirectly create an index on the column or make the column as the primary key column.
We are creating one new table with the CREATE command's help and inserting some values using the INSERT command.
Postgresql Data Generator Online No Human
In the below example, we are using the CREATE command to generate a Cars table into the Organization database:
Output
The Cars table has been successfully created after executing the above commands, as shown in the below screenshot:
Once the Cars table has been generated, we can insert some values into it using the INSERT command. And we can use the DEFAULT keyword in the INSERT command or omit the column name (Car_id).
Output
After implementing the above command, we will get the following message, and the value has been inserted successfully into the Cars table:
Free Postgresql
OR Using the DEFAULT Keyword with the Column name (Car_id):
Output
On implementing the above command, we will get the following message; the value has been inserted successfully into the Cars table:
As we can see in the above screenshot, the PostgreSQL inserted two rows into the Cars table with the Car_id column values are 1 and 2.
After creating and inserting the Cars table's values, we will use the SELECT command returns all rows of the Cars table:
Output
After successfully implementing the above command, we will get the following result:
We can use the pg_get_serial_sequence() function to get the sequence name of a SERIAL column in a specified table as we can see in the below syntax:
To get the current value created by the sequence, we can pass a sequence name to the currval() function.
In the following example, we used the currval() function to return the current value produced by the Cars table Car_id_seq object:
Output
After implementing the above command, we will get the below output:
We can use the RETURNING Car_id clause into the INSERT command if we want to get those values created by the sequence when we insert a new row into the table.
The below command is used to insert a new row into the Cars table and returns those records generated for the Car_id column.
Output
On executing the above command, we will get the following output, which returns the Car_id as 3:
Note:
- As we understood above, the sequence generator operation is not transaction-safe, which implies that each user will get a different value if two parallel database connections try to get the next value from a sequence.
- And the sequence number of that user will be idle and creates a gap in the sequence if one user can roll back the transaction.
Example2
Let us see one more example to learn the Serial pseudo-type Winzip 6 5 – mac edition of established compression utility. in detail.
So, we are going to create another new table as a Vegetables table with the help of the CREATE command into a similar database that is Organization with the Veg_id column as the SERIAL pseudo-type.
Output
The Vegetables table has been successfully created after executing the above commands, as shown in the below screenshot:
Once the Vegetables table has been generated, we will insert some values into it using the INSERT command, and omit the Veggies_id column as shown in the below command:
Output
We will get the following message on implementing the above command: the value has been inserted successfully into the Vegetables table.
Or, we can also use the Default keyword and uses the Veggie_id column as shown in the following command:
Output
After executing the above command, we will get the below message, which says that either we can use the Default keyword or the ignore the column name, we will get a similar output:
Therefore, we will add some more values to the Cars table with the help of following the command:
The issue with the above query arises when two cases are true, first you're charting your data over time and then two you have a week with no sign-ups. In the case of no sign-ups in a week you'd simply miss the 0 on your graph leaving a misleading impression. To smooth this out we go back to generate series and do an outer join on the week:
What other uses do you have for generate_series?
Postgres has a wealth of hidden gems within it. generate_series is just one of the handy built-in features of Postgres. If you know of other novel uses for it we'd love to hear about it @citusdata.
Enjoy what you're reading?
If you're interested in reading more posts from our team, sign up for our monthly newsletter and get the latest content delivered straight to your inbox.
In this section, we are going to understand the working of PostgreSQL Serial pseudo-type, which allows us to define auto-increment columns in tables. And we also see examples of the PostgreSQL Serial pseudo-type.
What is PostgreSQL Serial pseudo-type?
In PostgreSQL, we have one particular kind of database object generator known as Serial, which is used to create a sequence of Integers that are frequently used as a Primary key in a table.
The sequence can be generated with the help of the SERIAL pseudo-type, while we are creating a new table, as we can see in the following command:
The PostgreSQL does the following if we provide the SERIAL pseudo-type to the ID column:
- Firstly, PostgreSQL will create a sequence object and then establish the next value created by the sequence as the particular column's pre-defined value.
- After that, PostgreSQL will enhance a NOT NULL constraint to the ID column since a sequence always produces an integer that is a non-null value.
- At last, PostgreSQL will provide the owner of the sequence to the ID column; as an output, the sequence object is removed when the table or ID column is dropped.
Note: We can use both the command to specify the Serial pseudo-type as both the below command is similar to each other.
The PostgreSQL Serial pseudo-type has been classified into three types which are as follows:
- SMALLSERIAL
- SERIAL
- BIGSERIAL
We have the following table, which contains all the Serial pseudo-type specification that is supported by PostgreSQL:
| Name | Storage Size | Range |
|---|---|---|
| SMALLSERIAL | 2 bytes | 1 to 32767 |
| SERIAL | 4 bytes | 1 to 2147483647 |
| BIGSERIAL | 8 bytes | 1 to 9223372036854775807 |
Syntax of PostgreSQL Serial pseudo-type
The syntax of the PostgreSQL Serial pseudo-type as follows:
Examples of PostgreSQL SERIAL type
Let us see different examples to understand how the PostgreSQL Serial pseudo type works.
Note: We can define the PRIMARY KEY constraint for the SERIAL column because the SERIAL type does not indirectly create an index on the column or make the column as the primary key column.
We are creating one new table with the CREATE command's help and inserting some values using the INSERT command.
Postgresql Data Generator Online No Human
In the below example, we are using the CREATE command to generate a Cars table into the Organization database:
Output
The Cars table has been successfully created after executing the above commands, as shown in the below screenshot:
Once the Cars table has been generated, we can insert some values into it using the INSERT command. And we can use the DEFAULT keyword in the INSERT command or omit the column name (Car_id).
Output
After implementing the above command, we will get the following message, and the value has been inserted successfully into the Cars table:
Free Postgresql
OR Using the DEFAULT Keyword with the Column name (Car_id):
Output
On implementing the above command, we will get the following message; the value has been inserted successfully into the Cars table:
As we can see in the above screenshot, the PostgreSQL inserted two rows into the Cars table with the Car_id column values are 1 and 2.
After creating and inserting the Cars table's values, we will use the SELECT command returns all rows of the Cars table:
Output
After successfully implementing the above command, we will get the following result:
We can use the pg_get_serial_sequence() function to get the sequence name of a SERIAL column in a specified table as we can see in the below syntax:
To get the current value created by the sequence, we can pass a sequence name to the currval() function.
In the following example, we used the currval() function to return the current value produced by the Cars table Car_id_seq object:
Output
After implementing the above command, we will get the below output:
We can use the RETURNING Car_id clause into the INSERT command if we want to get those values created by the sequence when we insert a new row into the table.
The below command is used to insert a new row into the Cars table and returns those records generated for the Car_id column.
Output
On executing the above command, we will get the following output, which returns the Car_id as 3:
Note:
- As we understood above, the sequence generator operation is not transaction-safe, which implies that each user will get a different value if two parallel database connections try to get the next value from a sequence.
- And the sequence number of that user will be idle and creates a gap in the sequence if one user can roll back the transaction.
Example2
Let us see one more example to learn the Serial pseudo-type Winzip 6 5 – mac edition of established compression utility. in detail.
So, we are going to create another new table as a Vegetables table with the help of the CREATE command into a similar database that is Organization with the Veg_id column as the SERIAL pseudo-type.
Output
The Vegetables table has been successfully created after executing the above commands, as shown in the below screenshot:
Once the Vegetables table has been generated, we will insert some values into it using the INSERT command, and omit the Veggies_id column as shown in the below command:
Output
We will get the following message on implementing the above command: the value has been inserted successfully into the Vegetables table.
Or, we can also use the Default keyword and uses the Veggie_id column as shown in the following command:
Output
After executing the above command, we will get the below message, which says that either we can use the Default keyword or the ignore the column name, we will get a similar output:
Therefore, we will add some more values to the Cars table with the help of following the command:
Output
After executing the above command, we will get the below message, which displays that the value has been inserted successfully into the Vegetables table.
After creating and inserting the Vegetables table's values, we will use the SELECT command to return all rows of the Vegetables table:
Output
After successfully implementing the above command, we will get the below output:
Postgresql Data Compression
Overview
In the PostgreSQL Serial pseudo-type section, we have learned Serial pseudo-type functionality, which is mostly used to create an automatic increases column value for a particular table.
