1Z0-909 case studies
1Z0-909 · Put your knowledge to work in context.
The MySQL 8.0 Database Developer credential, exam code 1Z0-909, is an Oracle certification exam aimed at developers who build and maintain applications against MySQL 8.0 databases. It suits working developers, database engineers, and backend specialists who want a verifiable signal of practical MySQL 8.0 development skill rather than administration-only knowledge. The 1Z0-909 case studies are 5 cases and about 3,527 words.
1Indexing a JSON Path Without Changing the Document
An e-commerce catalog service stores product attributes in a JSON column. The product catalog table has 3.1 million rows and is defined as CREATE TABLE product catalog (id INT PRIMARY KEY, sku VARCHAR(32), attrs JSON, updated at DATETIME); .
661 words, about 3 min2Deadlocks in a Stock Transfer Procedure
A logistics application uses InnoDB and a stored procedure transfer stock(p sku, p from, p to, p qty) to move inventory between warehouses. The core table is stock(warehouse id INT, sku VARCHAR(32), qty INT, PRIMARY KEY (warehouse id, sku)) .
714 words, about 4 min3Top Two Products per Category with Ties
A sales analytics table has 22 million rows: CREATE TABLE sales (id BIGINT PRIMARY KEY, category id INT, product id INT, sold at DATETIME, revenue DECIMAL(12,2), KEY idx sold (sold at)); . The business wants the top two products per category by total revenue for the last 90 days.
762 words, about 4 min4A Job Queue That Serializes Workers
A background processing system uses InnoDB and a jobs table: CREATE TABLE jobs (id BIGINT AUTO INCREMENT PRIMARY KEY, status ENUM('queued','running','done','failed') NOT NULL, worker id INT NULL, updated at DATETIME, payload JSON, KEY idx status (status)); . Twelve workers each run START TRANSACTION; SELECT id FROM jobs WHERE status = 'queued' ORDER BY id LIMIT 1 FOR UPDATE; UPDATE jobs SET status = 'running', worker id = ?, updated at = NOW() WHERE id = ?; COMMIT; , then perform the job.
733 words, about 4 min5Implicit Conversion and Collation Mismatch
A customer database has 5 million rows: CREATE TABLE customers (id INT PRIMARY KEY, phone VARCHAR(20), email VARCHAR(255), created at DATETIME, KEY idx phone (phone), KEY idx email (email)) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4 0900 ai ci; . A legacy table legacy contacts stores email VARCHAR(255) CHARACTER SET utf8mb3 COLLATE utf8mb3 general ci .
657 words, about 3 min