SQL（Structured Query Language，结构化查询语言）是一种用于管理关系数据库的编程语言。以下是一些基本的SQL查询示例：
SELECT * FROM table_name;
SELECT column1, column2 FROM table_name;
SELECT * FROM table_name WHERE condition;
SELECT * FROM table_name ORDER BY column_name ASC|DESC;
SELECT column1, aggregate_function(column2) FROM table_name GROUP BY column1;
SELECT * FROM table1 JOIN table2 ON table1.column = table2.column;
SELECT * FROM table_name WHERE column IN (SELECT column FROM another_table);
UPDATE table_name SET column1 = value1, column2 = value2 WHERE condition;
DELETE FROM table_name WHERE condition;
INSERT INTO table_name (column1, column2) VALUES (value1, value2);
请注意，这些示例仅涵盖了SQL的基本功能。实际上，SQL提供了许多其他功能，如存储过程、视图、触发器等。要编写高效的SQL查询，需要熟悉数据库模式、索引、性能优化等方面的知识。
