Free SQL Help for Devs, DBAs, and the Curious

SQL, short for Structured Query Language, has been the de facto standard for interacting with relational databases for many years. However, with the advent of numerous database management systems like SQL Server 2019, MySQL 8.0, DB2 11.5, Azure SQL, and Azure Synapse, writing SQL queries that can run seamlessly across all these platforms has become a challenge. This post will guide you through the process of writing cross-platform SQL compatible queries.

To begin, it is important to understand that each of these platforms has its own set of SQL dialects. These dialects are extensions to the standard SQL, aimed at enhancing functionality specific to their respective platforms. However, the core SQL syntax remains largely the same across these platforms, thus forming the foundation for cross-platform compatible queries.

When writing cross-platform SQL queries, it is advisable to stick to the ANSI-SQL standard as much as possible. This is the standard SQL syntax that all platforms should support. For instance, a simple SELECT statement using ANSI-SQL may look like this:

SELECT column_name FROM table_name;

However, certain operations may require platform-specific syntax. For example, when limiting the number of records returned by the query, MySQL and DB2 use the LIMIT clause, while SQL Server uses the TOP keyword. In such cases, conditional code can be used to cater to each platform. Here's how you could do it:

-- MySQL/DB2
SELECT column_name FROM table_name LIMIT 10;

-- SQL Server
SELECT TOP 10 column_name FROM table_name;

It is also important to remember that different platforms may have different default settings for case sensitivity. For instance, SQL Server is case insensitive by default, whereas MySQL and DB2 are case sensitive. Therefore, it's a good practice to use consistent casing and avoid using case-sensitive object names.

Another key aspect to consider is the difference in data types across different platforms. An integer in MySQL is INT, but in SQL Server, it’s INTEGER. Date and Time data types also have differences across platforms. Therefore, when writing SQL queries, it's crucial to be aware of these differences and use the correct data types.

Writing SQL queries that are cross-platform compatible can be a daunting task due to the differences in dialects, case sensitivity, and data types among various platforms. However, by adhering to the ANSI-SQL standard, using conditional code for platform-specific operations, maintaining consistent casing, and using the correct data types, it can be achieved. Embrace these best practices and write more effective and efficient SQL queries that can run seamlessly across different platforms.