写出下列查询的SQL语句： 1) 查询计算机专业学生的姓名、年龄。 2) 查询计算机专业、年龄在18～20之间并且性别为“男”的学生的姓名、年龄。 3) 查找姓王的同学的所有信息。 4) 查询计算机专业学生的最大年龄和最小年龄。 5) 统计每个系的学生人数。 6) 统计男生、女生人数。

1) SELECT name, age FROM students WHERE major = '计算机';
2) SELECT name, age FROM students WHERE major = '计算机' AND age BETWEEN 18 AND 20 AND gender = '男';
3) SELECT * FROM students WHERE name LIKE '王%';
4) SELECT MAX(age), MIN(age) FROM students WHERE major = '计算机';
5) SELECT department, COUNT(*) AS student_count FROM students GROUP BY department;
6) SELECT gender, COUNT(*) AS gender_count FROM students GROUP BY gender;