Data Quality

Data quality in SQL Server // TRY_CONVERT for bit done safely — converting yes/no values

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Data quality starts with type conversion — and for bit columns it shows up right at the input value: yes/no information comes out of legacy sources in a wide variety of notations (‘J’, ‘Y’, ‘ON’, ‘1’, ‘x’, ‘-‘, …). SQL Server’s built-in TRY_CONVERT(bit, …) only covers the integer standard plus ‘true’/’false’ — everything else needs a dedicated conversion function. This article describes both: what’s built in, when … Read more

Data quality in SQL Server // TRY_CONVERT for float and real done safely

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Data quality with floating-point columns is a discipline of its own — and TRY_CONVERT(float, …) has a few quirks that tend to slip past the import path: an empty string becomes 0 (not NULL), a comma as decimal separator yields NULL, and even after a clean conversion 2 + 3.4 – 3.4 – 2 does not return exactly 0 as a float. This article sorts out the … Read more

Data quality in SQL Server // TRY_CONVERT for money and smallmoney done safely

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Anyone who has imported a point-of-sale report with values like ‘1.234,56 €’ from a CSV into a SQL Server database knows the pattern: TRY_CONVERT(money, ‘1,234.56’) yields 1234.5600. Yet TRY_CONVERT(money, ‘1.234,56’) yields NULL. And even when the import runs cleanly: money / 100 * 100 is not necessarily the same as the input value. At a glance — what this article covers: Prerequisite: SQL Server 2017+ (TRIM is used … Read more

Data Quality in an ETL Process — Catching Technical and Business Errors Before They Reach the Target System

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A single value that cannot be converted — a date in the wrong format, a number with the wrong decimal separator — and the entire ETL run aborts. Data quality in an ETL process means catching such errors proactively: identifying, logging and isolating them before they reach the target system. This article is the entry point to … Read more

Data quality in SQL Server // TRY_CONVERT for bigint, int, smallint and tinyint done safely

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Data quality starts with type conversion — and for integer columns, TRY_CONVERT has a few quirks that tend to slip past the import path: an empty string becomes 0 (not NULL), any decimal or thousands separator yields NULL, and a typed decimal is silently truncated — without rounding. This article sorts out the rules, shows the safe conversion pattern, and adds a … Read more

Data quality in SQL Server // TRY_CONVERT for decimal and numeric done safely

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Anyone who has watched a price import turn ‘123.45 €’ into a NULL instead of the expected decimal number knows the drill: TRY_CONVERT(decimal(5, 2), ‘123,45’) returns NULL, because a comma isn’t accepted as a decimal separator. And even with the comma gone, TRY_CONVERT(decimal(5, 2), ‘1234.56’) is also NULL — this time because of one integer digit too many. At a glance: Prerequisite: SQL Server 2017+ (TRIM in … Read more