Definition of Redshift Primary Key
Redshift provides different types of functionality to the user, in which that primary key is one of the functionalities that is provided by Redshift. Basically, Redshift supports the referential integrity constraint such as primary key, foreign key, and unique key. Basically, the primary key is one of the constraints and its uses during the table creation to identify the unique records from the table. Basically, there are two ways to define the constraint such as at the timetable creation and the second is that we can use an alter command to add the primary key constraint in an existing table as per user requirement. Basically, Redshift supports the referential integrity constraint such as primary key, foreign key, and unique key.
Basically, there are two ways to create the primary key in Redshift as follows. First, we can create a primary key during the table creation as follows.
create table table_name (colm name 1 data type(size), colm name 2 data type(size), colm name N data type(size) specified constraint name(Primary Key) (specified colm name));
In the above syntax, we use create table statement to create the table with primary key constraint as shown in the above syntax. Here we specify the different column names with different data types and their sizes as shown. At the end of syntax, we need to add the constraint name that is the primary key as per user requirements.
In a second way, we can use the alter command to add the primary key constraint into the existing table as follows.
alter table specified table name add specified constraint name primary key (specified colm name);
In the above syntax, we use alter table command to add the primary key into the existing table, in this syntax we need to pass the constraint name that is the primary key as well as the specified column name that we need to assign the primary key. Above mentioned syntax is depending on the user requirement that means as per user requirement we can use any one of the syntaxes.
How primary key works in Redshift?
Now let’s see how Primary Key works in Redshift as follows.
Basically, Uniqueness, primary key, and foreign key requirements are instructive just; they are not implemented by Amazon Redshift. Regardless, primary key and foreign keys are utilized as arranging clues and they ought to be announced if your ETL cycle or some other interaction in your application implements their trustworthiness.
For instance, the question organizer utilizes primary and foreign keys in certain measurable calculations. It does this to induce uniqueness and referential connections that influence subquery decorrelation strategies. By doing this, it can arrange enormous quantities of joins and wipe out excess joins.
The organizer uses these key connections, yet it expects that all keys in Amazon Redshift tables are substantial as stacked. On the off chance that your application permits invalid foreign keys or primary keys, a few inquiries could return erroneous outcomes. For instance, a SELECT DISTINCT inquiry may return copy lines if the primary key isn’t special. Try not to characterize key requirements for your tables on the off chance that you question their legitimacy. Then again, you ought to consistently announce primary and foreign keys and uniqueness requirements when you realize that they are legitimate.
Amazon Redshift authorizes NOT NULL segment imperatives.
Basically, the key constraint is used to identify the unique records and is also used as indexing as per user requirements. Being a columnar data set explicitly made for information warehousing, Redshift has an alternate treatment with regards to indexes. It doesn’t uphold standard records normally utilized in different data sets to cause inquiries to perform better. All types of keys work equally such as distkey, sortkey, these keys can apply more than one column as per requirement. Basically, Redshift is supported to create the primary key, unique key, and foreign key. In any case, similar documentation expresses that these are instructive just and are not implemented. It is prescribed to utilize them if your information stacking measure guarantees their honesty, as they are utilized as arranging clues to advance question execution. In any case, you ought not to characterize them on the off chance that you question their legitimacy. For instance, in case you don’t know whether the item name is truly extraordinary for a table, don’t make an interesting key limitation for it. In any case, on the off chance that you are sure, do make it so the information base motor can utilize it when executing your queries.
Now let’s see different examples of indexes in Redshift for better understanding as follows. Now let’s see the first way that is by using create table statements as follows.
create table product(
product_id int not null,
product_name varchar(255) not null,
product_cost decimal(15,2) not null,
primary key (product_id));
In the above example, we use create table statement to create the index during table creation as shown, in this example; we created a product table with different attributes with different data types as shown. Here we add the primary key on the product_id column name as shown. The final output or we can say the final result of the above statement we can illustrate by using the following screenshot as follows.
After the successful creation of the table, we are able to insert the unique values into a product table, here we assign a primary key on the product_id column that means product_id contains the only unique value but when we try to insert the same value at that time it shows an error message.
Now let’s see how we can use the alter table command to add the index in the existing table as follows.
Suppose we have a product table that we already created without any index and we need to add the index into that table at that time we can use the following statement as follows.
alter table product add primary key(product_id);
In the above example, we use the alter command to add the index into an existing table, here we added the primary key on the product_id column as shown. The final output or we can say the final result of the above statement we can illustrate by using the following screenshot as follows.
We hope from this article you learn more about the Redshift Primary Key. From the above article, we have learned the basic concept as well as the syntax of the Redshift Primary Key and we also see the different examples of the Redshift Primary Key. From this article, we learned how and when we use the Redshift Primary Key.
This is a guide to Redshift Primary Key. Here we discuss the definition, syntax, how Primary Key works in Redshift? and examples, respectively. You may also have a look at the following articles to learn more –