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Luka Matijević وبلاگ اضافه شد Coding
2025-05-31 20:25:35 -

An Efficient Way to Check for Existence of Multiple Values in SQL
What's faster, COUNT(*) or COUNT(*) with LIMIT in SQL? Let's check In a previous blog post, we’ve advertised the use of SQL EXISTS rather than COUNT(*) to check for existence of a value in SQL. I.e. to check if in the Sakila database, actors called WAHLBERG have played in any films, instead of: SELECT count(*) FROM actor a JOIN film_actor fa USING (actor_id) WHERE a.last_name =...

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Luka Matijević وبلاگ اضافه شد Coding
2025-05-31 20:25:33 -

Emulating SQL FILTER with Oracle JSON Aggregate Functions
How to implement FILTER semantics with Oracle JSON aggregate functions A cool standard SQL:2003 feature is the aggregate FILTER clause, which is supported natively by at least these RDBMS: ClickHouse CockroachDB DuckDB Firebird H2 HSQLDB PostgreSQL SQLite Trino YugabyteDB The following aggregate function computes the number of rows per group which satifsy...

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Luka Matijević وبلاگ اضافه شد Coding
2025-05-31 20:25:31 -

Think About SQL MERGE in Terms of a RIGHT JOIN
A SQL MERGE statement performs actions based on a RIGHT JOIN RIGHT JOIN is an esoteric feature in the SQL language, and hardly ever seen in the real world, because almost every RIGHT JOIN can just be expressed as an equivalent LEFT JOIN. The following two statements are equivalent: -- Popular SELECT c.first_name, c.last_name, p.amount FROM customer AS c LEFT JOIN payment AS p ON...

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Luka Matijević وبلاگ اضافه شد Coding
2025-05-31 20:25:30 -

When SQL Meets Lambda Expressions
A few modern SQL dialects have started introducing lambda expressions ARRAY types are a part of the ISO/IEC 9075 SQL standard. The standard specifies how to: Construct arrays Nest data into arrays (e.g. by means of aggregation or subqueries) Unnest data from arrays into tables But it is very unopinionated when it comes to function support. The ISO/IEC 9075-2:2023(E) 6.47...

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