DA0-002 Data Concepts and Environments Practice Question
A data engineer loads a CSV export into a table. The source system writes the value '007' for a product code, but after loading, an analyst queries the table and sees the value 7. The analyst needs the leading zero preserved for downstream matching against another system. Which action should the engineer take?
⚠ Common exam trap
The trap here is believing that a numeric display format or a derived expression can permanently restore a leading zero, when the stored data type itself has already discarded it.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Store the product code in a character or string column so the leading zero is retained
Product codes are identifiers, not quantities, so leading zeros are meaningful and must be preserved. Storing the value in a character column keeps '007' intact and allows reliable matching with other systems, whereas numeric storage strips the zero and presentation formats do not survive joins or exports.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a derived column that concatenates a literal zero with the numeric product code
Why it's wrong here
Concatenating a zero to a numeric value produces a new expression but does not fix the stored column, and it would add an extra zero to values that should not have one. Downstream systems still read the original numeric column. The clean fix is to store the identifier as text in the first place.
- ✗
Change the column data type to a numeric type with a display format that pads to three digits
Why it's wrong here
A numeric type does not preserve leading zeros at all; the padding is only a presentation format that many tools ignore or that is lost when the value is exported or joined. Downstream matching against a system that stores '007' as text would still fail. The value must be stored as text to retain the leading zero.
- ✗
Add a check constraint that rejects any product code shorter than three characters
Why it's wrong here
A check constraint validates values but does not change how they are stored. If the column is numeric, the value 7 still has no leading zero, and the constraint would either pass it or reject it without restoring the zero. The underlying problem is the data type, not the presence of validation rules.
- ✓
Store the product code in a character or string column so the leading zero is retained
Why this is correct
A character or string column treats '007' as a sequence of characters, preserving the leading zero exactly as written. This lets downstream matches against another system that uses the same textual code succeed. Since the code is an identifier rather than a quantity to calculate, storing it as text is the correct modeling choice.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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