Missing data in databases can cause bugs in applications or incorrect calculations. Recently, while working on a RETS application, I needed to ensure that not many missing values were encountered in one of the MySQL tables. Although one could easily write a SQL query to find the percentage of missing values, I many times find it easier to first get a visual representation of the amount of missing data there is in the table, and then drill-down further if required. One library that I found that lets you easily get a visual representation of missing data in your database tables is missingno – a Python library.
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Category: data
Pitfalls of assigning a wrong data type to a database column
A recent debugging session on a web application surfaced a recurrent issue in database design – that of assigning a wrong data type to a database field.
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Statistical distribution of column values in MySQL
Many times we need to get a statistical distribution of values in a database table. Say you have a e-commerce shoe store having a product table with the following fields and values. As this is only an example I’ve limited the table to a few items; there will hundreds of rows in a real-life table.
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Using the TOML configuration format in your applications
As any one who has programmed knows about configuration files. Configuration files are mostly text files used to configure the parameters and initial settings for computer programs – mostly user applications, operating system settings. Below is a small list of frequently used file formats.
– XML
– Windows INI
– YAML
– JSON
– toml
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Free datasets for testing database engines
Below is a small list of free datasets with which you can test your database queries or use it for learning and practicing sql query optimization or other things.
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Combinatorial row pairing in databases
While working on a database design I came across the problem of finding combinations or ‘cartesian product’ between all the rows between one table to another table, but not repeating the same permutations.
Take the ‘Teams’ table below which lists four cricket teams. We want to create a combination list of matches between each teams.
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