There are a few ways to compare two similar tables in SQL. Assuming PostgreSQL syntax, we might have this schema: CREATE TABLE t1 (a INT, b INT, c INT); CREATE TABLE t2 (a INT, b INT, c INT); INSERT INTO t1 VALUES (1, 2, 3), (4, 5, 6), (7, 8, 9); INSERT INTO t2 VALUES … Continue reading Use NATURAL FULL JOIN to compare two tables in SQL
Could we Have a Language That Hides Collections From Us?
I just fixed a bug. The fix required me to initialise an Object[] array with the init values for each type, instead of just null, i.e. false for boolean, 0 for int, 0.0 for double, etc. So, instead of just doing: Object[] converted = new Object[parameterTypes.length]; I needed: Object[] converted = new Object[parameterTypes.length]; for (int … Continue reading Could we Have a Language That Hides Collections From Us?
Using SQL Server FOR XML and FOR JSON Syntax on Other RDBMS With jOOQ
SQL Server supports transforming flat tabular SQL result sets into hierarchical structures by convention using the convenient FOR XML or FOR JSON syntaxes. This is really convenient and less verbose than the standard SQL/XML or SQL/JSON APIs - although the standard ones are more powerful. In this blog post, I'd like to show a few … Continue reading Using SQL Server FOR XML and FOR JSON Syntax on Other RDBMS With jOOQ
The Many Flavours of the Arcane SQL MERGE Statement
The SQL MERGE statement is a device whose mystery is only exceeded by its power. A simple example shows its full power according to standard SQL. Imagine you have a production table for product prices, and a staging table from which you want to load the latest prices. For once, I'm using the Db2 LuW … Continue reading The Many Flavours of the Arcane SQL MERGE Statement
What’s a “String” in the jOOQ API?
One of jOOQ's biggest strength is the fact that it is a type safe SQL API. "Type safe", in this context, means that every object that you put in a jOOQ query has a well defined type, such as: Condition Field Table These can be used in jOOQ in a type safe way as such: … Continue reading What’s a “String” in the jOOQ API?
Create Empty Optional SQL Clauses with jOOQ
When using jOOQ to create dynamic SQL statements (one of jOOQ's core value propositions), it is often necessary to add query elements conditionally, with a default "No-op" behaviour. For first time users, this default "no-op" behaviour is not always obvious as the jOOQ API is vast, and as with any vast API, there are many … Continue reading Create Empty Optional SQL Clauses with jOOQ
Using Java 13+ Text Blocks for Plain SQL with jOOQ
Most jOOQ users use the jOOQ DSL API, which provides compile time type safety and an easy way to write dynamic SQL. But occasionally, this DSL get in the way, because it might be Overkill for some very simple quick and dirty SQL queries Too limited when running very advanced vendor specific SQL, such as … Continue reading Using Java 13+ Text Blocks for Plain SQL with jOOQ
Never Concatenate Strings With jOOQ
jOOQ supports a vast amount of SQL syntax out of the box. As such, most users will not think of resorting to string concatenation like in the old days when writing dynamic SQL with JDBC. But every now and then, a vendor specific feature is not supported by jOOQ (yes, it happens). In that case, … Continue reading Never Concatenate Strings With jOOQ
5 Ways to Better Understand SQL by Adding Optional Parentheses
It appears that our recent beginner SQL articles explaining SQL syntax were quite popular. These include: A Beginner’s Guide to the True Order of SQL Operations A Probably Incomplete, Comprehensive Guide to the Many Different Ways to JOIN Tables in SQL 10 Easy Steps to a Complete Understanding of SQL How SQL DISTINCT and ORDER … Continue reading 5 Ways to Better Understand SQL by Adding Optional Parentheses
SQL DISTINCT is not a function
A very common misconception I often encounter with SQL users is the idea that DISTINCT is something like a function, and that it can take parenthesised arguments. Just recently, I've seen this Stack Overflow question where the OP was looking for a way to express this in jOOQ: SELECT DISTINCT (emp.id), emp.fname, emp.name FROM employee … Continue reading SQL DISTINCT is not a function