SQL Square Brackets []

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🔹 Introduction

In Salesforce Marketing Cloud Engagement (SFMC), SQL is based on SQL Server (T-SQL).

Square brackets [] are used to escape identifiers such as:

• Column names
• Data Extension names

This ensures SQL interprets them exactly as written.

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 Why [] Is Important

SQL normally expects:

• No spaces
• No special characters
• No reserved keywords

But in SFMC, real-world data often includes:

• Email Address
• Order-Amount
• Group

👉 Square brackets solve this by telling SQL:

“Use this exact name.”

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📌 Use Cases of []

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1️⃣ Column Names with Spaces

SELECT [First Name], [Email Address]
FROM Contacts
 
Original DE

Resultened DE 

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2️⃣ Reserved Keywords

SELECT [Date], [Group]
FROM Orders


Original DE




Final Result

 

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3️⃣ Special Characters

SELECT [Order-Amount], [Discount%]
FROM SalesData
 
 

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4️⃣ Data Extension Names

SELECT *
FROM [Customer Data 2025]



 

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5️⃣ Aliasing

SELECT 
    EmailAddress AS [Customer Email], 
    FirstName AS [Customer Name]
FROM Contacts

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⚙️ Practical SFMC Setup (Hands-On Practice)

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📂 Data Extension 1: Customer Orders

Field Name	Type
Email Address	EmailAddress
Order Date	Date
Order-Amount	Decimal
Discount%	Decimal
Group	Text

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📂 Data Extension 2: Contacts

Field Name	Type
Email Address	EmailAddress
First Name	Text

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👉 These DEs are designed to test:

• Spaces ✔
• Special characters ✔
• Reserved keywords ✔

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🚀 Real-Time Query Example

SELECT 
    [Email Address],
    COUNT(*) AS [Total Orders],
    MAX([Order Date]) AS [Last Order Date]
FROM [Customer Orders]
WHERE [Order Date] >= DATEADD(day, -30, GETDATE())
GROUP BY [Email Address]




 

📌 What this does:

1. FROM [Customer Orders]

👉 Starting point

• This tells SQL:

“Take data from the Customer Orders Data Extension”

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2. WHERE [Order Date] >= DATEADD(day, -30, GETDATE())

👉 Filtering logic (VERY IMPORTANT)

• GETDATE() → today’s date
• DATEADD(day, -30, GETDATE()) → 30 days back

👉 So this means:

“Only take orders from the last 30 days”

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3. SELECT [Email Address]

👉 This is your grouping key

• You are saying:

“I want results per customer (email)”

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4. COUNT(*) AS [Total Orders]

👉 Aggregation

• COUNT(*) = count number of rows (orders)

👉 Meaning:

“How many orders each customer placed”

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5. MAX([Order Date]) AS [Last Order Date]

👉 Another aggregation

• MAX() = latest value

👉 Meaning:

“What is the most recent order date for each customer”

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 6. GROUP BY [Email Address]

👉 The most important line

• This tells SQL:

“Group all rows by each email”

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🧠 Golden Rule

👉 Source DE = input data
👉 Target DE = output result

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⚠️ Common Mistakes

• Missing brackets
• Using reserved keywords without []
• Incorrect joins
• Trying to store aggregated data in same DE

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✅ Best Practices

• Avoid spaces in field names (if possible)
• Always use [] when unsure
• Keep naming consistent

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🎯 Interview Answer

Square brackets [] in SFMC SQL are used to escape identifiers such as column names or Data Extensions that contain spaces, special characters, or reserved keywords, ensuring queries execute correctly.

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🔥 Key Takeaway

👉 [] is critical for preventing SQL errors
👉 It ensures reliable and accurate queries