先学习NOT（逻辑非）用法。

#查询StudentBirthday非空列
SELECT * FROM "public"."Students" WHERE "StudentBirthday" IS NOT NULL;
#注意对比两个语句查询结果
SELECT "StudentBirthday" FROM "public"."Students" WHERE "StudentBirthday" IS NOT NULL;

排除非条件值

#不查询StudentSalary=2值
SELECT * FROM "public"."Students" WHERE "StudentSalary" NOT IN('2');
#对比查询语句
SELECT "StudentName","StudentAddress" FROM "public"."Students" WHERE "StudentSalary" NOT IN('2');

LIKE支持模糊查询，LIKE与两个通配符（%与_）一起使用，百分号表示零个，一个或多个字符。下划线代表一个单一字符。通配符可以被组合使用。ILIKE和LIKE 类似，LIKE区分大小写，ILIKE不区分。SIMILAR TO和LIKE有相似性，不过后者支持模糊查询同时还支持正则表达式。

先插入两条数据用于练习。

INSERT INTO "Students" VALUES (13, '杜牧', '0803-1-1', '陕西省西安市', 3);
INSERT INTO "Students" VALUES (14, '李商隐', '0817-1-1', NULL, NULL);

#查询所有杜姓人名，匹配单个字符
SELECT * FROM "public"."Students" WHERE "StudentName" LIKE '杜_';
#匹配多个字符，本例匹配StudentAddress列中含有陕西查询结果
SELECT "StudentName","StudentAddress" FROM "public"."Students" WHERE "StudentAddress" LIKE '%陕西%';