🚀 SAP ABAP Mock Interview — Question 3/50

 🎯 Time Complexity of Internal Table Operations

📋 Scenario

Consider the following code:

DATA: lt_mara TYPE TABLE OF mara.

SELECT *
  FROM mara
  INTO TABLE lt_mara.

LOOP AT lt_mara INTO DATA(ls_mara).

  READ TABLE lt_mara
    INTO DATA(ls_temp)
    WITH KEY matnr = ls_mara-matnr.

ENDLOOP.

❓ Question

1️⃣ What is the time complexity of this code?
2️⃣ How would you optimize it? Specifically explain:

• ✅ Standard Table
• ✅ Sorted Table
• ✅ Hashed Table

👉 And which one would you choose and why?

📊 Time Complexity Analysis

1️⃣ Standard Table 🔲
Default table type. READ TABLE performs linear search.

• LOOP → O(N)
• READ TABLE → O(N)
• Overall → O(N²) ⚠️

⚠️ Performance degrades badly for large datasets.

2️⃣ Sorted Table 📶
Data is sorted by key. READ TABLE uses binary search.

• LOOP → O(N)
• READ TABLE → O(log N)
• Overall → O(N log N)

⭐ Good choice when:

• Data must remain sorted
• Range access is required
• Partial key searches are common

3️⃣ Hashed Table #️⃣
Uses hash algorithm for key access.

• LOOP → O(N)
• READ TABLE → O(1)* (average case)
• Overall → O(N)

🚀 Best suited for:

• Frequent key-based lookups
• Exact key searches
• Large datasets

*(Average Case)

🏆 My Choice

If the requirement is purely key-based access using MATNR, I would choose a Hashed Table because lookup is approximately O(1), making the overall complexity O(N).

DATA lt_mara TYPE HASHED TABLE OF mara

  WITH UNIQUE KEY matnr.

✅ Fastest lookup for exact key access!

⚠️ Hidden Performance Issue

In this example, the READ TABLE is actually redundant.

💡 We are already looping over the same table, and the current record is already available in ls_mara.

❌ The additional READ TABLE provides no business value and only adds unnecessary processing.

🎓 Interview Tip

Many developers immediately answer:
👉 "Use a Hashed Table."

A stronger answer is:
👉 "First, I would question whether the READ TABLE is needed at all."

Removing unnecessary logic is often a bigger optimization than changing the table type.

💬 Bonus Question

Would you still choose a Hashed Table if the requirement involved:

• 🔍 Range searches
• 🔍 Partial key searches
• ↕️ Sorted output

Why or why not? Let's discuss in the comments! 👇

💡 Choose the right table type. Remove unnecessary logic. Write efficient ABAP.