CREATE INDEX index_name ON table_name
(column_name)
CREATE UNIQUE INDEX index_name ON table_name
(column_name)
用于在表的列上创建索引，以加速查询。
CREATE VIEW
CREATE VIEW view_name AS SELECT column_name(s)
FROM table_name WHERE condition
用于创建视图，以保存复杂查询的结果。
DELETE
DELETE FROM table_name WHERE some_column=some_value
DELETE FROM table_name
DELETE * FROM table_name
用于删除表中的记录，DELETE FROM table_name
和 DELETE * FROM table_name 会删除所有记录。
DROP DATABASE
DROP DATABASE database_name
用于删除数据库。
DROP INDEX
DROP INDEX table_name.index_name (SQL
Server)
DROP INDEX index_name ON table_name (MS
Access)
DROP INDEX index_name (DB2/Oracle)
ALTER TABLE table_name DROP INDEX index_name
(MySQL)
用于删除表上的索引。
DROP TABLE
DROP TABLE table_name
用于删除表及其所有数据。
GROUP BY
SELECT column_name, aggregate_function(column_name)
FROM table_name WHERE column_name operator
value GROUP BY column_name
用于按一个或多个列对结果集进行分组。
HAVING
SELECT column_name, aggregate_function(column_name)
FROM table_name WHERE column_name operator
value GROUP BY column_name HAVING aggregate_function(column_name)
operator value
用于对分组后的结果集进行过滤。
IN
SELECT column_name(s) FROM table_name
WHERE column_name IN (value1, value2, ...)
用于筛选匹配集合中某一值的记录。
INSERT INTO
INSERT INTO table_name VALUES (value1,
value2, ...)
INSERT INTO table_name (column1, column2,
...) VALUES (value1, value2, ...)
用于向表中插入新记录。
INNER JOIN
SELECT column_name(s) FROM table_name1
INNER JOIN table_name2 ON table_name1.column_name=table_name2.column_name
用于返回两个表中匹配的记录。
LEFT JOIN
SELECT column_name(s) FROM table_name1
LEFT JOIN table_name2 ON table_name1.column_name=table_name2.column_name
用于返回左表中的所有记录和右表中的匹配记录。
RIGHT JOIN
SELECT column_name(s) FROM table_name1
RIGHT JOIN table_name2 ON table_name1.column_name=table_name2.column_name
用于返回右表中的所有记录和左表中的匹配记录。
FULL JOIN
SELECT column_name(s) FROM table_name1
FULL JOIN table_name2 ON table_name1.column_name=table_name2.column_name
用于返回两个表中的所有记录，不论是否匹配。
LIKE
SELECT column_name(s) FROM table_name
WHERE column_name LIKE pattern
用于筛选匹配特定模式的记录。
ORDER BY
SELECT column_name(s)
FROM table_name
ORDER BY column_name [ASC|DESC]
用于对结果集进行排序。ASC 表示升序排列（默认），DESC 表示降序排列。
SELECT
SELECT column_name(s) FROM table_name
用于从表中选择数据。
SELECT
SELECT * FROM table_name
用于选择表中的所有列。
SELECT DISTINCT
SELECT DISTINCT column_name(s) FROM table_name
用于返回唯一不同的值。
SELECT INTO
SELECT * INTO new_table_name [IN externaldatabase]
FROM old_table_name
SELECT column_name(s) INTO new_table_name
[IN externaldatabase] FROM old_table_name
用于从一个表中选择数据并插入到新表中。
SELECT TOP
SELECT TOP number|percent column_name(s)
FROM table_name
ORDER BY column_name [ASC|DESC]
从表中返回前指定数量的记录，可以指定绝对数量或百分比。
TRUNCATE TABLE
TRUNCATE TABLE table_name
用于删除表中的所有数据，但不删除表结构。
UNION
SELECT column_name(s) FROM table_name1
UNION SELECT column_name(s) FROM table_name2
用于合并两个或多个 SELECT 语句的结果集，不包含重复记录。
UNION ALL
SELECT column_name(s) FROM table_name1
UNION ALL SELECT column_name(s) FROM table_name2
用于合并两个或多个 SELECT 语句的结果集，包含重复记录。
UPDATE
UPDATE table_name SET column1=value, column2=value,
... WHERE some_column=some_value
用于修改表中的现有记录。
WHERE
SELECT column_name(s) FROM table_name
WHERE column_name operator value
