The dialects of SQL in which we train

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The dialects of SQL in which we train
SQL comes in many dialects - the exact form of the language depends on whether you're using SQL Server, Oracle, Postgres, Snowflake or some other database. This blog lists the separate versions of SQL in which Wise Owl currently train.

Posted by Andy Brown on 18 September 2026

In this blog

The SQL dialects in which we train
Microsoft SQL Server's T-SQL
Oracle SQL
PostgreSQL
Snowflake SQL

As anyone living in the UK knows, dialect matters: if you're not from Glasgow or Newcastle a strong Glaswegian or Geordie accent can be hard to decipher. And so it is with SQL.

The comparison's not exact, because whether you're using Oracle, SQL Server, Snowflake, Postgres or some other relational database you will easily understand 90% of another database's SQL.

The SQL dialects in which we train

Wise Owl currently run training courses in 4 dialects of SQL (we used to offer a MySQL course, but this received no interest from our client base!):

Dialect	Notes
T-SQL	The dialect of SQL used for getting data out of Microsoft's SQL Server (and our first SQL love),
Oracle SQL	The SQL you'll use if you work with an Oracle database,
PostgreSQL	The SQL you will need to know if you're working with a Postgres database.
Snowflake SQL	The SQL dialect for getting data out of a Snowflake database.

Below are some notes on the idiosyncrasies of each dialect, to give you an idea of what the languages have in common (and what separates them).

Microsoft SQL Server's T-SQL

In truth we find it hard to see this as idiosyncratic, as it was for a long time the only dialect of SQL we taught in. However, I believe it's the only main SQL dialect which uses the TOP N keyword, such as in this example:

-- 10 most successful films

SELECT TOP 10

f.Title,

f.OscarWins

FROM

Film AS f

ORDER BY

f.OscarWins DESC

Oracle SQL

The oddest thing about Oracle SQL is the way in which it stores dates. For example Oracle would store Tom Cruise's birth date (3rd July 1962) in 7 bytes:

Byte	Part of date	For Tom Cruise
1	The second	Who knows?
2	The minute	Who knows?
3	The hour	Who knows?
4	The day	3
5	The month	7
6	The number of 256s in the year	7 (7 * 256 = 1792)
7	The year remainder	170 (the difference between 1962 and 1792)

PostgreSQL

One characteristic of PostgreSQL is the way it uses intervals so extensively. This feature also includes an amazing age function (well, amazing if you use other dialects of SQL) to give someone's true age. For example this query:

SELECT

a.full_name as Actor,

a.date_of_birth,

a.date_of_death,

-- actor's true age

age(

a.date_of_death,

a.date_of_birth

) AS "Actor Age"

FROM

actor as a

where

a.date_of_death is not null

Might give this result:

Notice how the interval automatically includes the years, months and days.

Snowflake SQL

Although you can use the CAST function in Snowflake to change the type of data, it's more common to use the :: operator. For example:

-- cast BookId to NUMBER and Title to VARCHAR with a fixed length

SELECT

b.BookId::NUMBER(38,0),

b.Title::VARCHAR(100)

FROM

Book AS b;

The weirdest thing about Snowflake is the way that it doesn't store relationships between tables or primary keys, but technically this is to do with the database and not the SQL language (you can still use joins to link tables together).

Some other pages relevant to this blog include:

You can also book hourly online consultancy for your time zone with one of our 7 expert trainers!

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