INNER JOIN-->return all rows from both tables where there is a match.

LEFT JOIN-->Return all rows from the first table, return rows from the second table where there is a match.

RIGHT JOIN-->Return all rows from the second table,return rows from the first table where there is a match.

UNION-->Selected columns need to have the same data type: eg. Employee_USA and Employee_UK. Select two or more columns, but get only one column for the results. With UNION, only distinct values are selected. With UNION ALL,all values are selected.
eg. SELECT employee_name FROM employee_Norway
          UNION ALL
          SELECT employee_name FROM employee_USA

ORDER BY-->eg. ORDER BY company DESC -->逆顺序
                               ORDER BY name ASC -->正顺序

IN-->SELECT column_name FROM table_name
            WHERE column_name IN (value1, value2,...)

BETWEEN-->Selects a range of data between two values, these values can be numbers, texts or dates.
SELECT column_name FROM table_name
WHERE column_name
BETWEEN value1 AND value2
eg. SELECT * FROM person WHERE lastname BETWEEN 'Hanson' and 'Peter'
The BETWEEN... AND operator is treated differently in different databases(involving including or excluding the test values), therefore it's important to check how the database treats "between and" operators. 所以如果你不确定的话，最好用 >= 和 <=.

CREATE-->创建 database:
    CREATE DATABASE database_name
      创建 table:
      CREATE TABLE table_name
      (
      column_name1 data_type,
      column_name2 data_type,
      ...
      )
      创建 index:    CREATE INDEX index_name
                            ON table_name (column_name)
      创建 stored procedure:    CREATE PROCEDURE procedure_name
      创建 view:    CREATE VIEW view_name AS
                           SELECT column_name(s)
                           FROM table_name
                           WHERE condition

VIEW-->a view is a virtual table based on the result-set of a select statement.You can add sql functions, WHERE and JOIN statements to a view and present the data as if the data were coming form a single table.The database does not store the view data, the database engine recreates the data each time.

使用View 的例子：

SELECT    DISTINCT
  tabcount.NumberOfTabs,
    rptform.FormID,
    rptform.Forename,
    rptform.IsPopUpFprm,
    rpt.form.IsConfirmRequired,
    ...
    ...
FROM    rptform
INNER JOIN    login
ON    rptform.LoginID=login.LoginID
INNER JOIN (SELECT
     COUNT(rptform.RptFormTabID) AS NumberOfTabs,
                 rptformtab.RptFormID
        FROM rptformtab
        GROUP BY rptformtab.RptFormID) tabcount
ON    tabcount.RptFormID = rptform.RptFormID

SELECT DISTINCT-->只选不重复的Rows.

DROP-->drop index-->SQL-->delete an index
                                               DROP INDEX table_name.index_name
                                -->Oracle-->delete an index
                                                  DROP INDEX index_name

            -->drop table-->删除table-->DROP TABLE table_name
            -->drop database-->删除databse-->DROP DATABASE database_name

TRUNCATE-->truncate table只删除table里面的data, table还在。

                    -->TRUNCATE TABLE table_name

LEFT(SQL的)-->LEFT (Character_expression, integer_expression)-->returns 从左数的n个跟Character_expression长得一样的字符。

           (ORACLE的)-->SUBSTR(Character_expression, 1 ,integer_expression)-->从左边

                               -->SUBSTR(Character_expression, -1 ,integer_expression)-->从右边

LEN(SQL的)-->LEN(string_expression)--> returns number of characters of the string.

         (ORACLE的)-->LENHTH(String_Expression)

PATINDEX(SQL的)-->PATINDEX('%pattern%',expression)

                    (ORACLE的)-->INSTR(String1,String2,[start_position],[appearence])-->return the nth appearence of string2 in string1. eg. INSTR(string1, string2)-->return the first appreance of string2 in string1.

DATE TIME CONVERTION

     SQL--> CONVERT(datetime, '2050-12-31 00:00:00', 120)

    ORACLE-->CONVERT('2050-12-31 00:00:00', 'YYYY-MM-DD HH:MI:SS')

GET RETURN CURRENT DATE

  SQL--> GETDATE()

    ORACLE-->CURRENT_DATE

DATE TIME OPERATION(例如时间倒退30秒)

  SQL-->DATEADD(SECOND, -30, @dShiftStartTIme)

    ORACLE-->dShiftStartTime - 30/86400 -->Oracle用的是一天，也就是如果 -1就是倒退一天

    1秒 = 1/86400

    1分钟 = 1/1440

    1小时 = 1/24

DATEDIFF

    SQL-->DATEDIFF('dd', '1999-01-01 00:00:00', '1999-12-20 00:00:00')

           -->应该会return 353,因为有353天between这两天。

    ORACLE-->1999-12-20 00:00:00 - 1999-01-01 00:00:00

NULL(如果是NULL return something else)

     SQL-->NULL(@ID,0) --> Convert @ID to 0 如果@ID是NULL

     ORACLE-->NVL(ID,0) --> Convert ID to 0 如果ID是NULL

SELECT TOP N

    SQL-->  SELECT TOP 1 rfToolCavityStatusID

                  FROM lkTSTC

    ORACLE--> SELECT rfToolCavityStatusID

                        FROM lkTSTC

                        WHERE ROWNUM = 1

UPDATE eg.

   UPDATE dbo.Users

    SET

          sUsername = xxx@xxx.com'

    WHERE

uiUserID = 'aaaaaaaaaaaaaa'
    AND

sUsername = 'yyy@yyy.com'

sContactEmailAddress = 'xxx@xxx.com',