SAP HANA is a database management tool that allows users and developers to analyze data sets with a variety of advanced methods. The features of the database let developers access and read the data in real-time. They can then use the data to craft unique business solutions for new applications.
The relational database uses the Structured Query Language. SQL is useful because it is standardized across platforms, powerful, and not dependent on any specific vendors. It is the main language within SAP HANA, and the database uses it to communicate or to store and retrieve data. Understanding the best practices of SQL in the SAP HANA database may help you use its features effectively.
Best Practices of SQL in the SAP HANA Database
This next section will detail some of the most useful practices for using SQL within SAP HANA. The items shown here are meant to simplify the SQL language or optimize how it communicates with the database.
If you feel like you need some more information on the topic before delving on the practices, you should check out our article on SAP HANA SLT Configuration.
Reduce the Complexity of Statements
SQLScript contains variables that allow you to break up a single complex statement into several simpler statements instead. This is one of the most basic best practices of SQL in the SAP HANA database.
Writing a long query as a single statement usually means you will need to use the ‘with’ definition in a temporary view or replicate a secondary query multiple times. Instead, you can break the statement into two queries and link those queries using variables within a table. The names you give to the table variables will lend meaning to the query and split it into more manageable chunks. This process makes the whole query easier to understand.
SQLScript contains a compilation tool that will combine the separate statements into a single query automatically when necessary. This makes an application easier to comprehend without negating its performance.
Identify Shared Sub-Expressions
As you work with SAP HANA and SQL, you will notice that many queries include common sub-expressions. Common sub-expressions may seem benign at first, but they can lead to repeated and unnecessary computations that tax system resources. Identifying these expressions whenever possible can cut down on costs and possibly optimize performance.
While query optimizers exist, it is difficult for most of them to detect common expressions within SQL queries. This is why it is a good idea to break up those queries into the smaller chunks we referenced in the previous section. The optimizers can read those smaller chunks and detect common sub-expressions. After that, they can detail more effective plans for those queries. You can utilize the ‘Explain’ plan to employ the Best practices of SQL in the SAP HANA database with regard to shared sub-expressions.
Understand Statement Costs
Understanding how much each statement costs the system is a basic part of the best practices of SQL in the SAP HANA database. While the operations within HANA are fast thanks to its in-memory features, every operation has costs that come with it, and some of those costs are higher than others.
A query plan may help you determine which calculations are going to be costly and how you can eliminate them. In some cases, you may be able to alter the formula for a given calculation to one that uses fewer resources within the system. A good rule of thumb is to remember that moving or duplicating data within the system has an associated cost. Even some processes designed to recognize duplicate data and alert you to it may have costs. Refining queries or statements so that move or process data only when necessary may help to reduce system costs.
SAP HANA contains a whole library of application functions for frequently used tasks. However, many of these tasks can be expensive. Your goal should be to reduce input as much as possible before you use them.
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Exploit the Engine
Exploiting the capabilities of various functions using SQLScript is a big part of the best practices of SQL in the SAP HANA database. You can use the Analytic view to model data from a star schema and allow HANA to use that schema to improve its computing performance.
If you are running an application that uses complex joins, you may wish to use Graphical Calculation or Attribute views to model the data. These views allow you to send additional information on the data structure that SAP HANA can exploit for better computing performance.
You can also exploit the engine by choosing not to assign a query result to the variable within a table. This will return a result set that includes the query back to the client. This can help you streamline the system as it won’t need to materialize the result on the server.
You may be able to execute multiple queries in tandem with one another to speed up the data processing. This parallelization is particularly noticeable with regard to the level of detail in a given set of data. You can process requests from several users at the same time using multiple cores. Additionally, you are able to execute different statements of an SQLScript if those statements operate independently.
Reducing dependencies between statements allows the system to operate more efficiently by running parallel operations. You can help the system do this by avoiding any variable references or imperative features.
Avoid Using Dynamic SQL
You can use dynamic SQL to craft SQL statements at a procedure’s execution time. It is one of the best ways to express the logic of an application. However, it is also slow because you will need to optimize your queries and perform checks on compile times with every startup of the procedure. It is part of best practices to use an alternative to dynamic SQL if one is available.
The above examples are some of the best practices of SQL in the SAP HANA database. The database is all about performing operations as quickly and efficiently as possible, and these tips may be able to help you do that. Please feel free to add your own tips in the section below.