SQL Beginner Lesson PF8

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    Beginner lesson plan for READ‑ONLY SQL, using the customers table.

    MenusSQL > SQL Column Lookup: You can search for table and column names:

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    1. Lesson Objective

    By the end of this lesson, learners will be able to:

    • Understand the purpose of a customer master table
    • Identify common customer‑related columns
    • Write basic SELECT queries using real table fields
    • Filter and sort customer data safely

    2. Introduction to the Customer Table (10 minutes)

    What This Table Represents

    • Stores customer master information
    • Contains:
      • Identifiers (cseq, ccode)
      • Names and contacts (cname, cfirst_name, clast_name)
      • Address and shipping details
      • Billing and credit data
      • Sales history and status flags

     

    3. Core Read‑Only SQL Command: SELECT (20 minutes)

    A. View All Customers (Basic Query)

    SELECT *
    FROM customers;

    Will give you all data from customer table.

     

    ⚠️ Use cautiously on large tables

    B. Select Specific Columns (Best Practice)

    SELECT
        cseq,
        ccode,
        cname,
        ccity,
        cstate,
        ccountry
    FROM customers

     

    Why this matters:

    • Faster queries
    • Easier to read
    • Safer for reporting

    C. Filter Results with WHERE

     

    SELECT
        ccode,
        cname,
        ccity,
        cstate
    FROM customers
    WHERE cstate = ‘CA’;

    Use cases:

    • Regional reports
    • State‑specific customers
    • Sales territory review

    D. Sorting Data with ORDER BY

    SELECT
        ccode,
        cname,
        cbalance
    FROM customers
    ORDER BY cbalance DESC;

    Shows:

    • Customers with the highest balances first
    • Useful for credit or accounts receivable review

    4. Common Read‑Only Customer Queries

    A. Find Active Customers

    SELECT
        ccode,
        cname,
        ccity,
        cstate
    FROM customers
    WHERE c_current = ‘1’;

    B. Customers with High Credit Limits

    SELECT
        ccode,
        cname,
        ccity,
        cstate
    FROM customers
    WHERE ccredit_limit>1000;

    C. Recently Added Customers

    SELECT
        ccode,
        cname,
        ccity,
        cstate,
         cinsert_date
    FROM customers
    ORDER BY cinsert_date DESC;

     

    5. Read‑Only Aggregations

    Count Total Customers

    SELECT COUNT(*) AS total_customers
    FROM customers;

     

    Count Customers by State

    SELECT     cstate,
    COUNT(*) AS customerscount
    FROM customers
    GROUP BY cstate
    ORDER BY customerscount DESC;

     

    6. Read‑Only SQL Safety Rules (10 minutes)

    ✅ Allowed Commands

    • SELECT
    • WHERE
    • ORDER BY
    • GROUP BY
    • COUNT, SUM, AVG

    Best Practices

    • Always start with few columns
    • Use filters when exploring data
    • Double‑check field names (many start with c_)

     

    Inserted 01/21/2026 – HS

     

    Updated on October 23, 2026

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