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Tag Archives: SQL

The 10 Most Popular DB Engines (SQL and NoSQL) in 2015

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About two years ago, we’ve published this post about the 10 most popular DB engines, where we analyzed the data published by Solid IT on their DB Ranking website. In the meantime, the Solid IT measurement system has found to be a credible source, such that the website has also been cited at Gartner, InfoWorld, and many other sources. Comparing ...

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You Probably don’t Use SQL INTERSECT or EXCEPT Often Enough

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When people talk about SQL JOIN, they often use Venn Diagrams to illustrate inclusion and exclusion of the two joined sets: While these Venn diagrams are certainly useful to understand (and remember) SQL JOIN syntax, they’re not entirely accurate, because SQL JOIN is a special type of a cartesian product, the CROSS JOIN. In a cartesian product between two sets ...

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Don’t Format Dates in SQL. Use the DATE Literal!

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I’m seeing people do this all the time. They want to hammer a date or timestamp constant into their SQL query, and the only function they know is the TO_DATE() or TO_TIMESTAMP() date parsing function: SELECT TO_DATE ('20150801', 'yyyymmdd') FROM DUAL; As observed in this Stack Overflow question, for instance: TO_DATE ('20150801', 'yyyymmdd') AS DAY_20150801_TOTAL, TO_DATE ('20150802', 'yyyymmdd') AS DAY_20150802_TOTAL, ...

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Passing Arrays to a PostgreSQL PL/pgSQL Function

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It can be handy to pass a collection of strings to a PL/pgSQL stored function via a PostgreSQL array. This is generally a very easy thing to accomplish, but this post demonstrates a couple of nuances to be aware of when passing an array to a PL/pgSQL function from JDBC or psql. The next code listing is for a contrived ...

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There is no Such Thing as Object-Relational Impedance Mismatch

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Much of the ORM criticism of the last decade missed the point, being inaccurate. By the end of this article, we will conclude with the following: There is no significant difference between the relational (data) model and object oriented models How to come to this conclusion? Read on! How we came to believe in this fallacy Many popular bloggers and ...

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Divided we Stand: Optional

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Our recent article “NULL is Not The Billion Dollar Mistake. A Counter-Rant” got us a lot of reads, controversial comments, and a 50/50 upvote / downvote ratio pretty much everywhere a blog post can be posted and voted on. This was expected. Objectively, NULL is just a “special” value that has been implemented in a variety of languages and type ...

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Use stored procedures with Hibernate

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This article show different ways to call stored procedures from hibernate. JDBC actions will not be covered. Postgresql will be used as a database. CREATE DATABASE example; CREATE TABLE company ( company_id BIGSERIAL PRIMARY KEY, name TEXT NOT NULL ); CREATE TABLE benefit ( benefit_id BIGSERIAL PRIMARY KEY, name TEXT, company_id BIGINT, CONSTRAINT fk_company FOREIGN KEY (company_id) REFERENCES company (company_id) ...

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Setting PostgreSQL psql Variable Based Upon Query Result

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When using PostgreSQL‘s psql command-line tool to interact with a PostgreSQL database via operator interaction or script, it is not uncommon to want to set psql variables based on the results of a particular query. While PostgreSQL’s procedural language PL/pgSQL supports approaches such as SELECT INTO and assignment (:=) to set PL/pgSQL variables based on a query result, these approaches ...

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Procedure-Like Functions in PostgreSQL PL/pgSQL

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PostgreSQL does not support stored procedures in the sense that a database such as Oracle does, but it does support stored functions. In this post, I look at a few tactics that can make the use of a stored function in PostgreSQL (stored function and its calling code both written in PL/pgSQL) feel like using a stored procedure. These simple ...

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Common SQL Clauses and Their Equivalents in Java 8 Streams

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Functional programming allows for quasi-declarative programming in a general purpose language. By using powerful fluent APIs like Java 8’s Stream API, or jOOλ’s sequential Stream extension Seq or more sophisticated libraries like javaslang or functionaljava, we can express data transformation algorithms in an extremely concise way. Compare Mario Fusco’s imperative and functional version of the same algorithm: Imperative vs. Functional ...

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