SQL Data Import Techniques and Tools
💡 Concept Name
SQL Data Import refers to loading external data—like CSV, Excel, or flat files—into a database using SQL tools or commands.
📘 Quick Intro
Whether you're working with CSVs, Excel sheets, or large datasets, SQL offers many ways to bring data into your tables: from GUI-based import wizards to advanced tools like SSIS, BCP, or scripting via BULK INSERT.
🧠 Analogy / Short Story
Think of a database as a library. Importing data is like unpacking boxes of new books and shelving them correctly. Depending on the method—manual, conveyor belt, or robot—the process varies in speed and control. Similarly, SQL offers manual and automated ways to bring in external data efficiently.
🔧 Technical Explanation
- BULK INSERT: Loads data from a file into a SQL table using a simple T-SQL command.
- BCP (Bulk Copy Program): Command-line tool for importing/exporting large datasets quickly.
- SSIS (SQL Server Integration Services): ETL tool for building complex, repeatable data import workflows.
- Import/Export Wizard: GUI-based tool in SSMS for quick file-based import.
- OPENROWSET: Queries external files (like Excel or CSV) directly as tables.
🎯 Purpose & Use Case
- ✅ Load data from legacy systems into SQL Server.
- ✅ Import Excel or CSV files into relational tables.
- ✅ Populate test data for dev environments.
- ✅ Set up recurring ETL processes using SSIS or jobs.
💻 Real Code Example
-- Using BULK INSERT
BULK INSERT Customers
FROM 'C:\Data\customers.csv'
WITH (
FIRSTROW = 2,
FIELDTERMINATOR = ',',
ROWTERMINATOR = '\n'
);
-- Using BCP (run in command line)
bcp MyDatabase.dbo.Customers in "C:\Data\customers.csv" -c -t, -S localhost -U sa -P password
❓ Interview Q&A
Q1: What is BULK INSERT used for?
A: To load data from a file directly into a SQL Server table using T-SQL.
Q2: How does BCP differ from BULK INSERT?
A: BCP is a command-line utility, whereas BULK INSERT is a SQL command.
Q3: What is SSIS used for?
A: It's used for ETL workflows including importing, transforming, and loading data.
Q4: Can you import Excel files into SQL Server?
A: Yes, using SSIS, Import Wizard, or OPENROWSET.
Q5: What are field terminators in BULK INSERT?
A: Characters that separate fields in the input file, e.g., commas for CSV.
Q6: What are the security considerations for data import?
A: Ensure proper file permissions, validate data to avoid injection or corruption.
Q7: How to handle headers in data files?
A: Use FIRSTROW=2 in BULK INSERT to skip header rows.
Q8: Can SSIS handle conditional logic during import?
A: Yes, SSIS supports advanced logic via control flows and script tasks.
Q9: What tool is best for one-time imports?
A: SSMS Import Wizard is quick and user-friendly for ad hoc imports.
Q10: What format must data be in for BULK INSERT?
A: Typically text-based files like CSV or TXT with consistent delimiters.
📝 MCQs
Q1. Which SQL command loads data from a file into a table?
- MERGE
- BULK INSERT
- INSERT INTO
- RESTORE
Q2. What is BCP in SQL Server?
- A trigger
- Backup command
- Command-line data copy tool
- Login utility
Q3. Which tool is used for building ETL workflows?
- SSRS
- SSMS
- SSIS
- BCP
Q4. What does FIELDTERMINATOR define?
- Date format
- Row size
- Character separating fields
- File name
Q5. Which method allows Excel import directly?
- TRUNCATE
- OPENROWSET
- CHECKPOINT
- RAISERROR
Q6. What is required for BULK INSERT to work?
- Stored procedure
- Cursor
- File path and format settings
- Temp table
Q7. What does FIRSTROW=2 mean?
- Start from row 2
- Skip 2 rows
- Skip header row
- End at row 2
Q8. Which is NOT a valid import method?
- BULK INSERT
- BCP
- SSIS
- DELETE INTO
Q9. What does SSMS stand for?
- SQL Script Management Suite
- Structured SQL Map Server
- SQL Server Management Studio
- Standard SQL Modeling System
Q10. Which tool offers visual drag-drop import features?
- BCP
- SSIS
- sqlcmd
- DBCC
💡 Bonus Insight
Always validate imported data using constraints and staging tables. For large files, consider batching inserts or disabling indexes temporarily for faster performance.
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