SELECT[ALL | DISTINCT | DISTINCTROW ][HIGH_PRIORITY][STRAIGHT_JOIN][SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT][SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]select_expr, ...[INTO OUTFILE 'file_name' export_options| INTO DUMPFILE 'file_name'][FROM table_references[WHERE where_definition][GROUP BY {col_name | expr | position}[ASC | DESC], ... [WITH ROLLUP]][HAVING where_definition][ORDER BY {col_name | expr | position}[ASC | DESC] , ...][LIMIT {[offset,] row_count | row_count OFFSET offset}][PROCEDURE procedure_name(argument_list)][FOR UPDATE | LOCK IN SHARE MODE]]

SELECT columna columnb FROM mytable;

SELECT college, region, seed FROM tournament  ORDER BY region, seed;
SELECT college, region AS r, seed AS s FROM tournament ORDER BY r, s;
SELECT college, region, seed FROM tournament  ORDER BY 2, 3;--要以相反的顺序进行分类，应把DESC（降序）关键字添加到ORDER BY子句中的列名称中。默认值为升序；该值可以使用ASC关键词明确地指定。
SELECT a, COUNT(b) FROM test_table ORDER BY a DESC；

SELECT a, COUNT(b) FROM test_table GROUP BY a DESC；
SELECT COUNT(col1) AS col2 FROM t GROUP BY col2 HAVING col2 = 2;-- HAVING不能用于应被用于WHERE子句的条目,不能编写如下语句：
SELECT col_name FROM tbl_name HAVING col_name > 0;
--而应该这么编写
SELECT col_name FROM tbl_name WHERE col_name > 0;--HAVING子句可以引用总计函数，而WHERE子句不能引用：
SELECT user, MAX(salary) FROM users GROUP BY user HAVING MAX(salary)>10;

SELECT * FROM tbl LIMIT 10;  # Retrieve rows 0-9;
SELECT * FROM tbl LIMIT 5,10;  # Retrieve rows 6-15;--如果要恢复从某个偏移量到结果集合的末端之间的所有的行，您可以对第二个参数是使用比较大的数。
--以下语句可以恢复从第96行到最后的所有行：
SELECT * FROM tbl LIMIT 95,18446744073709551615;

SELECT a,b,a+b INTO OUTFILE '/tmp/result.text'
FIELDS TERMINATED BY ','
OPTIONALLY ENCLOSED BY '"'
LINES TERMINATED BY '\n'
FROM test_table;

SELECT ...
UNION [ALL | DISTINCT]
SELECT ...
[UNION [ALL | DISTINCT]
SELECT ...]

(SELECT a FROM tbl_name WHERE a=10 AND B=1)
UNION
(SELECT a FROM tbl_name WHERE a=11 AND B=2)
ORDER BY a LIMIT 10;

SELECT DISTINCT a FROM table_name;
SELECT COUNT(DISTINCT a) FROM table_name;