在CentOS上使用Informix数据库时，编写查询语句的基本语法与其他关系型数据库（如MySQL、PostgreSQL）类似。以下是一些常见的Informix查询语句示例：
SELECT * FROM table_name;
SELECT column1, column2 FROM table_name;
SELECT * FROM table_name WHERE condition;
例如，查询age大于30的记录：
SELECT * FROM users WHERE age > 30;
SELECT * FROM table_name ORDER BY column_name [ASC|DESC];
例如，按age降序排列：
SELECT * FROM users ORDER BY age DESC;
SELECT column1, COUNT(*) FROM table_name GROUP BY column1;
例如，按department分组并计算每个部门的员工数量：
SELECT department, COUNT(*) AS employee_count FROM employees GROUP BY department;
SELECT a.column1, b.column2 FROM table1 a
JOIN table2 b ON a.common_column = b.common_column;
例如，连接employees和departments表：
SELECT e.name, d.department_name FROM employees e
JOIN departments d ON e.department_id = d.id;
SELECT a.column1, b.column2 FROM table1 a
LEFT JOIN table2 b ON a.common_column = b.common_column;
SELECT a.column1, b.column2 FROM table1 a
RIGHT JOIN table2 b ON a.common_column = b.common_column;
SELECT column1 FROM table1 WHERE column2 IN (SELECT column2 FROM table2);
例如，查询employees表中department_id在departments表中的记录：
SELECT name FROM employees WHERE department_id IN (SELECT id FROM departments);
INSERT INTO table_name (column1, column2) VALUES (value1, value2);
例如，向users表插入一条记录：
INSERT INTO users (name, age) VALUES ('John Doe', 30);
UPDATE table_name SET column1 = value1 WHERE condition;
例如，更新users表中age大于30的记录：
UPDATE users SET age = age + 1 WHERE age > 30;
DELETE FROM table_name WHERE condition;
例如，删除users表中age大于60的记录：
DELETE FROM users WHERE age > 60;
希望这些示例能帮助你在CentOS上使用Informix数据库编写查询语句。如果有更多具体问题，欢迎继续提问！