Technology Tips

One use case that happens often in SQL is the need to retrieve today’s date. This could be you are doing an analysis based on recent data, or it could be you are building a script that needs to retrieve the date dynamically.

Unfortunately there is no standard SQL that allows you to retrieve today’s date across different database systems. So in this post we have gathered the SQL statement needed to retrieve today’s date for the most popular database systems:

Oracle

SELECT SYSDATE FROM DUAL;

SQL Server

SELECT GETDATE();

MySQL

SELECT CURDATE();

DB2

SELECT current date FROM sysibm.sysdummy1;

Hive

SELECT CURRENT_DATE;

SparkSQL

SELECT CURRENT_DATE or SELECT CURRENT_DATE();

BigQuery

SELECT CURRENT_DATE;

PostgreSQL

SELECT CURRENT_DATE;

SQLite

SELECT DATE();

Technically the answer is yes, it is possible to have multiple WHERE clauses in a SQL statement. For example, if you are using a subquery, you can certainly employ a WHERE clause within the subquery, and then again in the outer query. Another example is when you are combining two SQL statements with a UNION / UNION ALL / INTERSECT / MINUS. In this case, both SQL statements can have their own WHERE clause.

Continue reading →

Sometimes when you look at other people’s SQL code, you’ll see 

WHERE 1=1

as part of the code. If you haven’t seen this before, you might be wondering why people do this. After all, 1=1 always evaluates to TRUE, so that apparently makes this line of code redundant. As it turns out, there are two reasons why this is done:

Reason 1: Testing

Continue reading →

For data-related roles such as data scientists or data analysts, one of the interviews will inevitably be on SQL. This makes sense because SQL is what you use to extract data from databases, and as such is considered as an important fundamental skill set for the role.

One question people generally ask is, “How do I prepare for a SQL interview?” Here we will provide the answer to that question. We’ll start of with the general format of a SQL interview, then go into how to prepare for the interview, and finally we provide a few tips on what to do during the actual interview.

General format

In a SQL interview, the first five minutes or so will be spent on doing introductions. For this part, you should have a short script ready (no more than two minutes) that goes into your background and why you are interested in the role.

Continue reading →