*所有表格缨叫、列的名稱都不能包含空格或者關(guān)鍵字褐捻,比如select, table等
*所有改變都不能撤銷捺檬,刪除或者改變表中的值時可以先用SELECT來確認(rèn)要改變的值是否正確
SELECT:
一般格式:
SELECT (DISTINCT) col_name, COUNT(), AVG(), MIN(), MAX(), SUM() AS alias FROM table_name
(WHERE ... LIKE 'some_pattern')
(GROUP BY ... HAVING 用來在group by 結(jié)果中搜索的分句)
(ORDER BY col_name1, col_name2 DESC)
CREATE :
一般格式:
CREATE TABLE tablename(
column_name data_type attributes...,
column_name data_type attributes...,
)
INSERT:(插入行)
一般格式:
INSERT INTO table_name
VALUES (按照列的順序輸入每個值预明,注意數(shù)據(jù)類型)
或
INSERT INTO table_name (col1, col2, ...)
VALUES (按照上面所說的列順序輸入值)
UPDATE:(改變表中的值)
一般格式:
UPDATE table_name
SET col_name = new_value, ...
WHERE col_name = some_value
DELETE:(刪除行)
一般格式:
DELETE FROM table_name
WHERE col_name = some_value?? #此行不寫的話就會刪除所有行采转,慎重慎重
DROP:(刪除表)
一般格式:
DROP TABLE table_name