Nesting Collections With jOOQ 3.14’s SQL/XML or SQL/JSON support
One of the main features of ORMs is M as in Mapping. Libraries like jOOQ help auto-mapping flat or nested database records onto Java classes that have the same structure as the SQL result set. The...
View ArticleAutomatically Transform Oracle Style Implicit Joins to ANSI JOIN using jOOQ
While jOOQ is mostly being used as an internal SQL DSL for embedded, dynamic SQL in Java, where it offers the best solution on the market, jOOQ is increasingly also used for one of its secondary...
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jOOQ Internals: Pushing up SQL fragments
Over the past 13 years, jOOQ has accrued quite some internal features, which you, the user, are not exposed to. One very interesting feature is the capability for any arbitrary jOOQ expression tree...
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Implementing a generic REDUCE aggregate function with SQL
So, @rotnroll666 nerd sniped me again. Apparently, the Neo4j Cypher query language supports arbitrary reductions, just like any functional collection API, oh say, the JDK Stream API: Stream.of(2, 4,...
View ArticleTranslating Stored Procedures Between Dialects
In the past years, we’ve invested a lot of effort into improving our procedural language capabilities in jOOQ. What started with a simple internal API to support the emulations of DDL clauses like...
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Calculating Pagination Metadata Without Extra Roundtrips in SQL
When paginating results in SQL, we use standard SQL OFFSET .. FETCH or a vendor specific version of it, such as LIMIT .. OFFSET. For example: SELECT first_name, last_name FROM actor ORDER BY actor_id...
View ArticleUse IN List Padding to Your JDBC Application to Avoid Cursor Cache Contention...
A problem few developers are aware of is the possibility of running into “cursor cache contention” or “execution plan cache contention” problems when using IN lists in SQL. The problem that is...
View ArticleHow to Get an RDBMS Server Version with SQL
Do you need to know what RDBMS Server version you’re on, and you only have SQL at your disposal? No problem. Most RDBMS provide you with that information in some form of meta data table. Here’s how:...
View ArticlejOOQ 3.15’s New Multiset Operator Will Change How You Think About SQL
This is how SQL should have been used all along. They called it The Third Manifesto, ORDBMS, or other things. Regrettably, it never really took off. Because most vendors didn’t adopt it. And those who...
View ArticleReactive SQL with jOOQ 3.15 and R2DBC
One of the biggest new features of the recently released jOOQ 3.15 is its new support for reactive querying via R2DBC. This has been a highly popular feature request, and we finally delivered on it....
View ArticleStandard SQL/JSON – The Sobering Parts
It’s been almost 1 year now since jOOQ 3.14 was released in October 19, 2020 with SQL/JSON (and SQL/XML) support. Half a year later, we’ve released jOOQ 3.15 with MULTISET support, which builds on top...
View ArticleFormatting ASCII Charts With jOOQ
A very little known feature in jOOQ is the Formattable.formatChart() capability, which allows for formatting any jOOQ result as an ASCII chart. This can be useful for quick plotting of results in your...
View ArticleVendor Agnostic, Dynamic Procedural Logic with jOOQ
One of the strengths of modern RDBMS is the capability to mix the powerful SQL language with procedural code. SQL is a 4th generation programming language (4GL), and as such, extremely well suited for...
View ArticleThe jOOQ Parser Ignore Comment Syntax
jOOQ’s parser can’t parse every possible SQL syntax. Try this random PostgreSQL syntax: ALTER SYSTEM RESET ALL And the jOOQ parser will complain: DOMAIN, INDEX, SCHEMA, SEQUENCE, SESSION, TABLE, TYPE,...
View ArticleFunctional Dependencies in SQL GROUP BY
The SQL standard knows an interesting feature where you can project any functional dependencies of a primary (or unique) key that is listed in the GROUP BY clause without having to add that functional...
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PostgreSQL 14’s enable_memoize For Improved Performance of Nested Loop Joins
I’ve recently discovered a pleasant new addition to PostgreSQL 14, the new enable_memoize flag that improves the performance of some nested loop joins where statistics hint at this being appropriate....
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Fun with PostGIS: Mandelbrot Set, Game of Life, and More
The upcoming jOOQ 3.16 will finally offer support for the various RDBMS GIS extensions via issue #982. This is great news per se, and will be covered in a future blog post, when the integration is...
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Why You Should Use jOOQ With Code Generation
I’m answering many jOOQ questions on Stack Overflow, and a lot of times. The problem has the same cause: People not using jOOQ’s code generator. The main reason people seem not to be using it, is...
View ArticleThe Useful BigQuery * EXCEPT Syntax
One of the coolest things about using and making jOOQ is that we get to discover the best extensions to the standard SQL language by vendors, and add support for those clauses in jOOQ via emulations....
View ArticleUsing jOOQ’s DiagnosticsConnection to detect N+1 Queries
N+1 queries are a popular problem in many applications that run SQL queries. The problem can be described easily as follows: 1 query fetching a parent value is runN queries fetching each individual...
View ArticleA Rarely Seen, but Useful SQL Feature: CORRESPONDING
I recently stumbled upon a standard SQL feature that was implemented, to my surprise, in HSQLDB. The keyword is CORRESPONDING, and it can be used with all set operations, including UNION, INTERSECT,...
View ArticleApproximating e With SQL
If you’re running on PostgreSQL, you could try the following cool query: WITH RECURSIVE r (r, i) AS ( SELECT random(), i FROM generate_series(1, 1000000) AS t (i) ), s (ri, s, i) AS ( SELECT i, r, i...
View ArticleUse MULTISET Predicates to Compare Data Sets
Questions that might be a bit more difficult to solve using ordinary SQL are questions of the kind: What films have the same actors as a given film X? As always, we're using the sakila database for...
View ArticleVarious Meanings of SQL’s PARTITION BY Syntax
For SQL beginners, there's a bit of an esoteric syntax named PARTITION BY, which appears all over the place in SQL. It always has a similar meaning, though in quite different contexts. The meaning is...
View ArticleHow to Fetch Sequence Values with jOOQ
A lot of RDBMS support standard SQL sequences of some form. The standard SQL syntax to create a sequence is: CREATE SEQUENCE s; The following is how you could fetch a value from this sequence, using...
View ArticleNested Transactions in jOOQ
Since jOOQ 3.4, we have an API that simplifies transactional logic on top of JDBC in jOOQ, and starting from jOOQ 3.17 and #13502, an equivalent API will also be made available on top of R2DBC, for...
View ArticleHow to Typesafely Map a Nested SQL Collection into a Nested Java Map with jOOQ
A really cool, recent question on Stack Overflow was about how to map a nested collection into a Java Map with jOOQ. In the past, I've blogged about the powerful MULTISET operator many times, which...
View ArticleSetting the JDBC Statement.setFetchSize() to 1 for Single Row Queries
An interesting hint by Vladimir Sitnikov has made me think about a new benchmark for jOOQ: https://twitter.com/lukaseder/status/1407662449331949568 The benchmark should check whether single row queries...
View ArticleThe Many Different Ways to Fetch Data in jOOQ
The jOOQ API is all about convenience, and as such, an important operation (the most important one?) like fetch() must come with convenience, too. The default way to fetch data is this:...
View ArticleChanging SELECT .. FROM Into FROM .. SELECT Does Not “Fix” SQL
Every now and then, I see folks lament the SQL syntax's peculiar disconnect between the lexical order of operations (SELECT .. FROM) the logical order of operations (FROM .. SELECT) Most recently here...
View ArticleThe Performance of Various To-Many Nesting Algorithms
It's been a while since jOOQ 3.15 has been released with its revolutionary standard SQL MULTISET emulation feature. A thing that has been long overdue and which I promised on twitter a few times is to...
View ArticleHow to Filter a SQL Nested Collection by a Value
I stumbled upon a very interesting question on Stack Overflow about how to use jOOQ's MULTISET operator to nest a collection, and then filter the result by whether that nested collection contains a...
View ArticleCreate Dynamic Views with jOOQ 3.17’s new Virtual Client Side Computed Columns
One of jOOQ 3.17's coolest new features are client side computed columns. jOOQ 3.16 already added support for server side computed columns, which many of you appreciate for various reasons. What's a...
View ArticleUsing H2 as a Test Database Product with jOOQ
The H2 database is an immensely popular in-memory database product mostly used by Java developers for testing. If you check out the DB-Engines ranking, it ranks 50th, which is quite impressive, as this...
View ArticleA Condition is a Field
Starting with jOOQ 3.17, the Condition type extends the Field<Boolean> type. Because, that's what the SQL standard thinks it is, in sorts: <boolean value expression> ::= <predicate>...
View ArticleHow to Plot an ASCII Bar Chart with SQL
No need for expensive Tableau subscriptions. Ditch Microsoft Excel. Just use native PostgreSQL to quickly visualise your data! Here's an idea I had for a while. As you may know, jOOQ can produce fancy...
View ArticleLATERAL is Your Friend to Create Local Column Variables in SQL
The standard SQL WITH clause has been tremendously helpful in structuring SQL queries. Instead of nesting everything in unreadable derived tables like this: SELECT actor_id, name, COUNT(*) FROM (...
View ArticleWhen to Use jOOQ and When to Use Native SQL
A frequently encountered doubt people have when using jOOQ is to decide when a "complex" query should be written using jOOQ API vs. when it should be implemented using native SQL. The jOOQ manual is...
View ArticleEmulating Window Functions in MySQL 5.7
One of MySQL 8's biggest improvements is the support of window functions. As I always said in conferences, there's SQL before window functions and SQL after window functions. Once you start using them,...
View ArticleThe Performance Impact of SQL’s FILTER Clause
I've found an interesting question on Twitter, recently. Is there any performance impact of using FILTER in SQL (PostgreSQL, specifically), or is it just syntax sugar for a CASE expression in an...
View ArticleHow to Write a Derived Table in jOOQ
One of the more frequent questions about jOOQ is how to write a derived table (or a CTE). The jOOQ manual shows a simple example of a derived table: In SQL: SELECT nested.* FROM ( SELECT AUTHOR_ID,...
View ArticleHow to Turn a List of Flat Elements into a Hierarchy in Java, SQL, or jOOQ
Occasionally, you want to write a SQL query and fetch a hierarchy of data, whose flat representation may look like this: SELECT id, parent_id, label FROM t_directory; The result might be: |id...
View ArticleMaven Coordinates of the most popular JDBC Drivers
Do you need to add a JDBC driver to your application, and don't know its Maven coordinates? This blog post lists the most popular drivers from the jOOQ integration tests. Look up the latest versions...
View ArticleWorkaround for MySQL’s “can’t specify target table for update in FROM clause”...
In MySQL, you cannot do this: create table t (i int primary key, j int); insert into t values (1, 1); update t set j = (select max(j) from t) + 1; The UPDATE statement will raise an error as follows:...
View ArticlejOOQ 3.19’s new Explicit and Implicit to-many path joins
jOOQ 3.19 finally delivers on a set of features that will greatly simplify your queries further, after jOOQ 3.11 introduced implicit to-one joins: Explicit path joins To-many path joins Implicit join...
View ArticleA Hidden Benefit of Implicit Joins: Join Elimination
One of jOOQ's key features so far has always been to render pretty much exactly the SQL that users expect, without any surprises - unless some emulation is required to make a query work, of course....
View ArticleAn Efficient Way to Check for Existence of Multiple Values in SQL
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...
View ArticleGetting Top 1 Values Per Group in Oracle
I've blogged about generic ways of getting top 1 or top n per category queries before on this blog. An Oracle specific version in that post used the arcane KEEP syntax: SELECT max(actor_id) KEEP...
View ArticleEmulating SQL FILTER 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...
View ArticleThink About SQL MERGE in Terms of 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...
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