Does anyone really know what time it is? First we have the bare bones of the PostgreSQL Interval, Date and Timestamp Data types. Here are the questions: What types are they? And what options do they have? What postgresql.conf variables affect date and time i/o? Available Date and Time Data types Date day of year […]
Elein is a PostgreSQL enthusiast and contributes regularly to 2ndQuadrant blog.
Entries by Elein
Postgresql String Functions and Operators. This blog today is going to talk about strings: how they are stored, how they are input, and lots of examples of how to use string operators and functions in order to manipulate them. Strings, strings, strings. What we are not going to cover is regular expressions, although we […]
The problem: duplicate rows Once upon a time, there was a database person who knows about referential integrity and its importance for creating database tables. The interesting part is that referential integrity, including primary keys, enable keeping with the standard of not having duplicate rows. However, they just wanted a private little table on their […]
Some people go to great lengths to avoid GROUP BY and HAVING clauses in their queries. The error messages are fussy but they are usually right. GROUP BY and HAVING key words are essential for good SQL reporting. The primary reason for GROUP BY is to reduce the number of rows, usually by aggregation. It […]
LATERAL The primary feature of LATERAL JOIN is to enable access elements of a main query in a subquery which can be very powerful. Several common uses of LATERAL are to: denormalize arrays into parent child tables aggregation across several tables row or action generation. Note, however, that the subquery will execute for each main […]