- 01Getting Started
- 02SELECT Statement Basics
- 03Filtering Rows with WHERE
- 04Sorting Results with ORDER BY
- 05Combining Tables with JOIN
- 06Aggregating Data with GROUP BY
- 07Fuzzy Matching with LIKE
- 08Modifying Data with INSERT, UPDATE, and DELETE
- 09Introduction to Subqueries
- 10Creating a VIEW
- 11Ranking Rows with Window Functions
- 12Understanding Transactions
- 13Writing Comments in SQL
- 14Logical Operators: AND, OR, NOT
- 15Working with NULL Values
- 16INNER JOIN vs. LEFT JOIN
- 17Filtering Aggregates with HAVING
- 18Removing Duplicates with DISTINCT
- 19Combining Results with UNION
- 20Conditional Values with CASE
- 21Checking Existence with EXISTS
- 22Changing Table Structure with ALTER TABLE
- 23Self Joins
- 24Speeding Up Searches with INDEX
- 25GROUP BY with Multiple Columns
- 26Pagination with LIMIT and OFFSET
- 27Pattern Matching with GLOB
- 28Date Calculations with the date() Function
- 29Joining Three Tables
- 30Matching Multiple Values with IN
- 31Derived Tables: Subqueries in FROM
- 32The Basics of TRIGGER
- 33Readable Queries with WITH (CTEs)
- 34UPSERT: Insert or Update in One Statement
- 35Combining MIN, MAX, and AVG
- 36Restricting Input with CHECK Constraints
- 37Auto-Numbering with AUTOINCREMENT
- 38Inspecting Query Plans with EXPLAIN QUERY PLAN
- 39ORDER BY with Multiple Columns
- 40Conditional Aggregation with CASE
- 41Removing Objects with DROP TABLE and DROP VIEW
- 42Combining Multiple CTEs
- 43Date Range Search with BETWEEN
- 44Finding What's Missing with NOT EXISTS
- 45Substituting NULL with COALESCE
- 46String Functions: UPPER, LENGTH, and SUBSTR
- 47Converting Types with CAST
- 48Merging Grouped Values with GROUP_CONCAT
- 49Enforcing Integrity with FOREIGN KEY
- 50Capstone: Build a Mini Library Management System
String Functions: UPPER, LENGTH, and SUBSTR
This lesson covers string functions — UPPER, LENGTH, and SUBSTR — so you can clean up inconsistent text data. It's for anyone searching "SQL string functions tutorial."
SQL also has functions for manipulating text: UPPER(column) converts to uppercase, LENGTH(column) gets the character count, and SUBSTR(column, start, length) extracts part of a string.
The example applies UPPER(), LENGTH(), and SUBSTR(code, 1, 3) to a product code, all as separate columns in the same result — a good look at combining several string functions in one SELECT.
A common early mistake is miscounting the starting position for SUBSTR() — SQL's string functions typically count the first character as position 1, so if you're used to 0-based indexing from another language, results tend to land one character off from what you expect. Extracting the first few characters of a product code, or normalizing case before comparing values, are the kind of text-cleanup tasks this handles well — and the feel is quite similar to string handling in general-purpose programming languages once you get used to it.
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