Subqueries and joining tables - your indispensable SQL tools

In today's landscape, data precision has become pivotal in #decision-making. Strategic subqueries (aka nested queries) and joining tables (aka join clause) in #SQL are indispensable for professionals aiming to explore, analyze, and extract meaningful insights.

The power of SQL in data precision

Today's systems are able to automate very complex business activities. To support these processes, data often needs to be divided into smaller pieces to avoid redundancy, ensure data consistency, and maximize processing time.This is known as the normalization of tables.

Our business analysts are experts in manipulating the tables, linking them via subqueries or combining them using join clauses, such as putting the focus on data that is meaningful, business and functionally wise.

Subqueries vs. Join Clauses

While both techniques allow highlighting entries common between tables, subqueries are the go-to technique for formulating non-association conditions that cannot be expressed otherwise. A subquery has to be utilized for example when listing the names of the customers who did not buy a specific gift for Christmas (non-association).

However, joining tables offers the flexibility to display and aggregate data based on the attributes contained in any of the tables linked via this technique. For example, if the result of the query has to return attributes (columns) that come from multiple source tables, a join clause must be used. If the query must count the number of Christmas gifts bought by each customer, it will be required to join all the tables where the attributes to be displayed and aggregated are stored.

In terms of performance, subqueries are only marginally faster to execute when dealing with large sets of data.

Conclusion

In an environment where every detail matters, these techniques become indispensable tools for business analysts committed to generating accurate and relevant insights.??

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Credits to David Laguesse