MySQL 速查表
一份可搜索、可打印的 MySQL 参考——查询、连接、索引、函数、数据类型和管理命令。免费。
Querying
10SELECT * FROM users;
Select all columns and rows
SELECT id, name FROM users;
Select specific columns
SELECT DISTINCT city FROM users;
Unique values only
WHERE age > 18 AND active = 1
Filter rows by conditions
WHERE name LIKE 'A%'
Pattern match (% = any chars)
WHERE id IN (1, 2, 3)
Match any value in a set
WHERE age BETWEEN 18 AND 30
Inclusive range filter
ORDER BY created_at DESC
Sort descending
LIMIT 10 OFFSET 20
Paginate results
WHERE email IS NULL
Match null values
Joins
8INNER JOIN orders ON orders.user_id = users.id
Rows matching in both tables
LEFT JOIN orders ON ...
All left rows + matches
RIGHT JOIN orders ON ...
All right rows + matches
CROSS JOIN colors
Cartesian product
SELF JOIN: FROM emp e JOIN emp m ON e.mgr = m.id
Join a table to itself
USING (user_id)
Join on a same-named column
UNION / UNION ALL
Combine result sets
SELECT u.*, o.total FROM users u JOIN orders o
Alias tables for clarity
Aggregation
9COUNT(*)
Count rows
SUM(amount)
Total of a numeric column
AVG(price)
Average value
MIN(price), MAX(price)
Smallest and largest
GROUP BY country
Group rows for aggregation
HAVING COUNT(*) > 5
Filter on aggregated groups
GROUP_CONCAT(name)
Concatenate grouped values
COUNT(DISTINCT city)
Count unique values
ROW_NUMBER() OVER (ORDER BY id)
Window function ranking
Modifying data
8INSERT INTO users (name) VALUES ('Sam');
Insert a single row
INSERT INTO users (name) VALUES ('A'),('B');
Insert multiple rows
UPDATE users SET active = 1 WHERE id = 5;
Update matching rows
DELETE FROM users WHERE id = 5;
Delete matching rows
TRUNCATE TABLE logs;
Remove all rows quickly
INSERT ... ON DUPLICATE KEY UPDATE
Upsert on a unique key
REPLACE INTO users ...
Delete + insert on conflict
INSERT IGNORE INTO ...
Skip rows that would error
Schema / DDL
9CREATE TABLE users (id INT PRIMARY KEY);
Create a new table
AUTO_INCREMENT
Auto-numbering column
ALTER TABLE users ADD COLUMN age INT;
Add a column
ALTER TABLE users DROP COLUMN age;
Remove a column
ALTER TABLE users MODIFY name VARCHAR(100);
Change a column type
DROP TABLE IF EXISTS users;
Delete a table
FOREIGN KEY (user_id) REFERENCES users(id)
Reference another table
ON DELETE CASCADE
Cascade deletes to children
CREATE TABLE t2 LIKE t1;
Copy a table structure
Indexes & keys
8PRIMARY KEY (id)
Unique row identifier
UNIQUE (email)
Enforce unique values
CREATE INDEX idx_name ON users (name);
Speed up lookups on a column
CREATE INDEX idx_ab ON t (a, b);
Composite (multi-column) index
DROP INDEX idx_name ON users;
Remove an index
FULLTEXT (body)
Full-text search index
EXPLAIN SELECT ...;
Show the query plan
SHOW INDEX FROM users;
List indexes on a table
Data types
9INT, BIGINT, TINYINT
Integer types by size
DECIMAL(10, 2)
Exact fixed-point numbers
VARCHAR(255)
Variable-length string
TEXT, LONGTEXT
Large text blobs
DATE, DATETIME, TIMESTAMP
Date and time types
BOOLEAN (TINYINT(1))
True/false stored as 0/1
JSON
Native JSON document column
ENUM('a', 'b')
One of a fixed set of values
UNSIGNED
Non-negative numeric modifier
Type sizes & limits
20TINYINT
1 byte: -128..127 (0..255 UNSIGNED)
SMALLINT
2 bytes: -32,768..32,767 (0..65,535)
MEDIUMINT
3 bytes: -8.39M..8.39M (0..16.78M)
INT
4 bytes: -2.15B..2.15B (0..4.29B)
BIGINT
8 bytes: ±9.22×10^18 (0..1.84×10^19)
DECIMAL(M, D)
Exact: M up to 65 digits, D up to 30
FLOAT / DOUBLE
4 / 8 bytes approximate floating point
CHAR(M)
Fixed length, 0..255 characters
VARCHAR(M)
0..65,535 bytes (shared 64KB row limit)
TINYTEXT
Up to 255 bytes (~255 chars)
TEXT
Up to 65,535 bytes (64 KB)
MEDIUMTEXT
Up to 16,777,215 bytes (16 MB)
LONGTEXT
Up to 4,294,967,295 bytes (4 GB)
BLOB types
TINY/—/MEDIUM/LONG: 255B..4GB (binary)
JSON
Stored as LONGBLOB, up to ~4 GB
ENUM / SET
ENUM: 65,535 members; SET: 64 members
DATE
1000-01-01 to 9999-12-31 (3 bytes)
DATETIME
1000 to 9999, microseconds (5–8 bytes)
TIMESTAMP
1970-01-01 to 2038-01-19 UTC (4 bytes)
TIME / YEAR
±838:59:59 / 1901..2155
Functions
9NOW(), CURDATE()
Current datetime / date
DATE_FORMAT(d, '%Y-%m-%d')
Format a date
DATEDIFF(a, b)
Days between two dates
CONCAT(a, ' ', b)
Join strings
COALESCE(a, b, 'n/a')
First non-null value
IFNULL(x, 0)
Replace null with a default
CASE WHEN x > 0 THEN '+' ELSE '-' END
Conditional expression
CAST(x AS CHAR)
Convert a value type
ROUND(x, 2)
Round to decimals
Transactions & admin
9START TRANSACTION;
Begin a transaction
COMMIT;
Persist the transaction
ROLLBACK;
Undo the transaction
SAVEPOINT sp1;
Set a rollback point
SHOW TABLES;
List tables in the database
DESCRIBE users;
Show a table structure
SHOW PROCESSLIST;
List running connections
GRANT ALL ON db.* TO 'u'@'%';
Grant user privileges
mysqldump -u root db > db.sql
Back up a database (CLI)
没有条目匹配“:q”。
关于 MySQL 速查表
这份 MySQL 速查表将你实际会用到的 SQL 汇集到一个可搜索的参考页面中：查询、连接（JOIN）、聚合、修改数据、模式与 DDL 语句、索引与键、带大小和限制的数据类型、内置函数，以及事务和管理命令。
它既可作为语法提醒——例如 LEFT JOIN、UPSERT 或 ALTER TABLE 的准确写法——也可用于查阅没人会去死记硬背的细节，比如整数范围、VARCHAR 限制，以及哪种索引类型适合某个查询。
和本工具的每份速查表一样，它免费且在客户端运行：用搜索框实时过滤各行，通过固定的目录在章节间跳转，一键复制任意语句，打印页面留作桌边参考。
如何使用 MySQL 速查表
- 打开速查表，浏览各章节，从"查询"和"连接"到"模式/DDL"，再到"事务与管理"。
- 搜索关键词如 JOIN、INDEX 或 GROUP BY，实时过滤所有代码片段。
- 当你需要存储细节而非语法时，可跳转到"数据类型"或"类型大小与限制"。
- 点击某条语句或其复制图标，将 SQL 复制到剪贴板。
- 使用"打印"获取整份 MySQL 参考资料的纸质版本。
常见问题
十个章节，涵盖查询、连接、聚合、数据修改、模式 DDL、索引与键、数据类型、类型大小与限制、函数，以及事务和管理命令——每个都是可直接复制的 SQL 代码片段。
是的。专门有一个章节列出了类型大小和限制——那些原本需要在手册中查阅的整数范围和字符串长度上限——紧挨在数据类型章节旁边。
可以。点击 SQL 代码片段或其所在行的复制图标，即可立即复制到剪贴板。
两者都可以。搜索框会在你输入时实时过滤每一行，并显示匹配计数，打印按钮会输出一个没有页面外壳的整洁版本。
是的，完全免费，在你的浏览器中运行，无需登录。
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