Question

We’re looking to populate a number of tables for testing. The data can all be the same except for a timestamp column. Other columns in the row contain complicated data, like objects in xml format and other messy stuff, so we don’t want to have to remake it. What would be an easy way to expand a single entry to thousands, by incrementing a timestamp by a constant interval, through a sql query.

Our current idea (in a C-ish pseudocode) is to:

Get the latest (likely only) row and store it in a variable "thisRow"
While(thisRow->time < endTime)
{
Increment thisRow->time by a constant variable
Insert thisRow
}

We are using postgres

Answer 1

I like to keep a Numbers table in my databases for certain queries. If you had one then you could use the single statement below. If you don’t have one, it’s easy enough to generate one as a temporary table or permanent table.

INSERT INTO Test_Table
(
     col1,
     col2,
     ...,
     my_timestamp
)
SELECT
     ST.col1,
     ST.col2,
     ...,
     DATEADD(mi, N.number, ST.my_timestamp)
FROM
     Source_Table ST
INNER JOIN Numbers N ON
     N.number BETWEEN 1 AND 1000  -- Change this to what you want

This is for SQL Server. The DATEADD function may be different in your RDBMS. You can also add in a random function if you don’t want the intervals to be exactly one minute and you could of course change the intervals to be hours, days, or whatever. You could also use a simple equation if you wanted say two hours per interval.