SQL Beginner and Common Query Quick Reference
A Chinese SQL study guide organized around databases, tables, filters, joins, aggregation, updates and a local troubleshooting workflow.
Learn queries through result sets
This guide introduces table structure, basic queries, joins, aggregation, data changes and troubleshooting. Read each statement together with its result rows, field meaning and relationship between tables instead of memorizing syntax alone.
Practice locally and inspect relationships
Start with a small local database and fictional rows. Before joins and aggregation, understand primary keys and one-to-many relationships; duplicate rows often indicate an incomplete join condition or a hidden cardinality expansion.
Treat writes as change operations
Run UPDATE, DELETE and DROP only in a practice database, transaction or verified backup. Confirm the WHERE clause and expected affected rows before committing, and keep a script and result record for every exercise.
Save to your cloud drive
Save the complete collection first so files remain together and are easier to access across devices.
Quark Cloud Drive
RecommendedSave SQL Beginner and Common Query Quick Reference to this cloud drive
Baidu Netdisk
Save SQL Beginner and Common Query Quick Reference to this cloud drive
SQL beginner query workflow
Extract the examples, create a local practice database, move from SELECT to joins and aggregation, and use execution plans to investigate unexpected results.
Before you start
- Prepare MySQL or a compatible database, a client and a separate practice schema.
- Understand tables, rows, columns, primary keys and basic data types.
- Use fictional data and a rollback-capable script directory.
Quick start
- 01
Inspect the chapters
Extract the ZIP, read the directory order and choose the SQL type for the first exercise.
- 02
Create practice tables
Build a few local tables and record field types, primary keys and relationships between them.
- 03
Start with SELECT
Practice filtering, sorting, limits, joins, grouping and aggregation while checking row counts and field meaning.
- 04
Troubleshoot with plans
Shrink the data set, check conditions and join keys, inspect indexes and then use the execution plan for slow or unexpected queries.
Usage tips
- Run write statements in a transaction or copy, and verify WHERE conditions and affected rows before UPDATE, DELETE or DROP.
- Check one-to-many relationships before aggregation so totals are not inflated by duplicate rows.
- Database versions, functions, pagination and licenses may differ; verify them in the active environment.
Troubleshooting and uninstall
What if a join creates duplicate rows?
Inspect the relationship and join condition, query each table separately and verify whether one-to-many expansion is expected.
What if the SQL syntax is rejected?
Locate the nearby keyword, bracket or quote, then confirm that the example's SQL dialect matches the current database.
Frequently asked questions
Which SQL statements should beginners learn first?
Start with SELECT, WHERE, ORDER BY and LIMIT, then add joins, grouping, aggregation and data changes.
Why do joins produce repeated rows?
A one-to-many relationship or incomplete join condition can expand rows, so inspect keys and row counts before aggregation.
How should UPDATE and DELETE be practiced?
Use an isolated database or transaction, confirm the WHERE clause and check the expected affected rows before committing.
Does the SQL work in every database?
Basic syntax is shared, while functions, pagination and data types vary across MySQL and other dialects.