WHERE
SELECT column01[, column02, column03...] FROM table_name WHERE condition;
WHERE与ORDER BY配合的时候，order by在where后面。
比较符
WHERE中的条件，有很多比较符，可提的就是!=与<>是一个意思，表示不等于。
BETWEEN AND
WHERE column_name BETWEEN start AND end;
WHERE column_name >= start and column_name <=end; --这俩等价
检查为空
WHERE column_name IS NULL; --- IS NOT NULL
WHERE AND / WHERE OR
WHERE AND优先级比WHERE OR高，结合使用有顺序要求的，使用括号。
即
WHERE condition01 OR condition02 AND condition03;
-- 与
WHERE condition01 OR (condition02 AND condition03); -- 是等价的。AND优先级比OR要高。
WHERE IN
其实就是简写的OR
例如：
WHERE price in(10, 11, 4);
NOT
WHERE NOT condition; -- 否定条件
NOT IN(...);
NOT BETWEEN AND;
NOT EXISTS;
LIKE
WHERE name LIKE '%z_'; --%表示n个字符，_表示一个字符
