SQLServer常见查询问题



http://bbs.csdn.net/topics/340078327

1.生成若干行记录

--自然数表1-1M
CREATE TABLE Nums(n int NOT NULL PRIMARY KEY CLUSTERED)
--书上介绍了很多种填充方法，以下是最高效的一种，需要SS2005的ROW_NUMBER()函数。
WITH B1 AS(SELECT n=1 UNION ALL SELECT n=1), --2
B2 AS(SELECT n=1 FROM B1 a CROSS JOIN B1 b), --4
B3 AS(SELECT n=1 FROM B2 a CROSS JOIN B2 b), --16
B4 AS(SELECT n=1 FROM B3 a CROSS JOIN B3 b), --256
B5 AS(SELECT n=1 FROM B4 a CROSS JOIN B4 b), --65536
CTE AS(SELECT r=ROW_NUMBER() OVER(ORDER BY (SELECT 1)) FROM B5 a CROSS JOIN B3 b) --65536 * 16
INSERT INTO Nums(n)
SELECT TOP(1000000) r FROM CTE ORDER BY r

2.日历表

CREATE TABLE Calendar(
	date datetime NOT NULL PRIMARY KEY CLUSTERED,
	weeknum int NOT NULL,
	weekday int NOT NULL,
	weekday_desc nchar(3) NOT NULL,
	is_workday bit NOT NULL,
	is_weekend bit NOT NULL
)
GO
WITH CTE1 AS(
	SELECT
		date = DATEADD(day,n,'19991231')
	FROM Nums
	WHERE n <= DATEDIFF(day,'19991231','20201231')),
CTE2 AS(
	SELECT
		date,
		weeknum = DATEPART(week,date),
		weekday = (DATEPART(weekday,date) + @@DATEFIRST - 1) % 7,
		weekday_desc = DATENAME(weekday,date)
	FROM CTE1)
--INSERT INTO Calendar
SELECT
	date,
	weeknum,
	weekday,
	weekday_desc,
	is_workday = CASE WHEN weekday IN (0,6) THEN 0 ELSE 1 END,
	is_weekend = CASE WHEN weekday IN (0,6) THEN 1 ELSE 0 END
FROM CTE2

3.字符串的拼接(Join)与切分(Split)

<strong>--将一组查询结果按指定分隔符拼接到一个变量中
DECLARE @Datebases varchar(max)
SET @Datebases = STUFF((
		SELECT ','+name
		FROM sys.databases
		ORDER BY name
		FOR XML PATH('')),1,1,'')
SELECT @Datebases
--将传入的一个参数按指定分隔符切分到一个表中
DECLARE @SourceIDs varchar(max)
SET @SourceIDs = 'a,bcd,123,+-*/=,x&y,<key>'
SELECT v = x.n.value('.','varchar(10)')
FROM (
    SELECT ValuesXML = CAST('<root>' +
        REPLACE((SELECT v = @SourceIDs FOR XML PATH('')),',','</v><v>') +
        '</root>' AS XML)
) t
CROSS APPLY t.ValuesXML.nodes('/root/v') x(n)
</strong>

<strong>--测试数据：
CREATE TABLE #ToJoin(
    TableName varchar(20) NOT NULL,
    ColumnName varchar(20) NOT NULL,
    PRIMARY KEY CLUSTERED(TableName,ColumnName))
GO
CREATE TABLE #ToSplit(
    TableName varchar(20) NOT NULL PRIMARY KEY CLUSTERED,
    ColumnNames varchar(max) NOT NULL)
GO
INSERT INTO #ToJoin VALUES('tblEmployee','EmployeeCode')
INSERT INTO #ToJoin VALUES('tblEmployee','EmployeeName')
INSERT INTO #ToJoin VALUES('tblEmployee','HireDate')
INSERT INTO #ToJoin VALUES('tblEmployee','JobCode')
INSERT INTO #ToJoin VALUES('tblEmployee','ReportToCode')
INSERT INTO #ToJoin VALUES('tblJob','JobCode')
INSERT INTO #ToJoin VALUES('tblJob','JobTitle')
INSERT INTO #ToJoin VALUES('tblJob','JobLevel')
INSERT INTO #ToJoin VALUES('tblJob','DepartmentCode')
INSERT INTO #ToJoin VALUES('tblDepartment','DepartmentCode')
INSERT INTO #ToJoin VALUES('tblDepartment','DepartmentName')
GO
INSERT INTO #ToSplit VALUES('tblDepartment','DepartmentCode,DepartmentName')
INSERT INTO #ToSplit VALUES('tblEmployee','EmployeeCode,EmployeeName,HireDate,JobCode,ReportToCode')
INSERT INTO #ToSplit VALUES('tblJob','DepartmentCode,JobCode,JobLevel,JobTitle')
GO

--拼接(Join)，SQL Server 2005的FOR XML扩展可以将一个列表转成一个字串：
SELECT
    t.TableName,
    ColumnNames = STUFF(
        (SELECT ',' + c.ColumnName
        FROM #ToJoin c
        WHERE c.TableName = t.TableName
        FOR XML PATH('')),
        1,1,'')
FROM #ToJoin t
GROUP BY t.TableName

--切分(Split)，使用SQL Server 2005对XQuery的支持：
SELECT
    t.TableName,
    ColumnName = c.ColumnName.value('.','varchar(20)')
FROM (
    SELECT
        TableName,
        ColumnNamesXML = CAST('<Root>' + REPLACE((SELECT ColumnName = ColumnNames FOR XML PATH('')),',','</ColumnName><ColumnName>') + '</Root>' AS xml)
    FROM #ToSplit
) t
CROSS APPLY t.ColumnNamesXML.nodes('/Root/ColumnName') c(ColumnName)
</strong>

4.树形结构的存储与查询

--测试数据
CREATE TABLE #Employees(
	EmployeeCode varchar(20) NOT NULL PRIMARY KEY CLUSTERED,
	ReportToCode varchar(20) NULL)
GO
INSERT INTO #Employees VALUES('A',NULL)
INSERT INTO #Employees VALUES('B','A')
INSERT INTO #Employees VALUES('C','A')
INSERT INTO #Employees VALUES('D','A')
INSERT INTO #Employees VALUES('E','B')
INSERT INTO #Employees VALUES('F','B')
INSERT INTO #Employees VALUES('G','C')
INSERT INTO #Employees VALUES('H','D')
INSERT INTO #Employees VALUES('I','D')
INSERT INTO #Employees VALUES('J','D')
INSERT INTO #Employees VALUES('K','J')
INSERT INTO #Employees VALUES('L','J')
INSERT INTO #Employees VALUES('M','J')
INSERT INTO #Employees VALUES('N','K')
GO
/*
可能遇到的查询问题：
1. 员工'D'的所有直接下属
2. 员工'D'的所有2级以内的下属（包括直接下属和直接下属的下属）
3. 员工'N'的所有上级（按报告线顺序列出）
4. 员工@EmployeeCode的所有@LevelDown级以内的下属（@EmployeeCode和@LevelDown以变量传入）
DECLARE @EmployeeCode varchar(20), @LevelDown int;
SET @EmployeeCode = 'D';
SET @LevelDown = 2;
5. 员工@EmployeeCode的所有@LevelUp级以内的上级（@EmployeeCode和@LevelUp以变量传入）
DECLARE @EmployeeCode varchar(20), @LevelUp int;
SET @EmployeeCode = 'N';
SET @LevelUp = 2;
*/
--用递归CTE实现员工树形关系表
WITH CTE AS(
	SELECT
		EmployeeCode,
		ReportToCode,
		ReportToDepth = 0,
		ReportToPath = CAST('/' + EmployeeCode + '/' AS varchar(200))
	FROM #Employees
	WHERE ReportToCode IS NULL
	UNION ALL
	SELECT
		e.EmployeeCode,
		e.ReportToCode,
		ReportToDepth = mgr.ReportToDepth + 1,
		ReportToPath = CAST(mgr.ReportToPath + e.EmployeeCode + '/' AS varchar(200))
	FROM #Employees e
	INNER JOIN CTE mgr
	ON e.ReportToCode = mgr.EmployeeCode
)
SELECT * FROM CTE ORDER BY ReportToPath

5.IPv4地址的存储与查询

<strong>--测试数据
CREATE TABLE #IPs(
	strIP varchar(15) NULL,
	binIP binary(4) NULL)
GO
INSERT INTO #IPs VALUES('0.0.0.0',NULL)
INSERT INTO #IPs VALUES('255.255.255.255',NULL)
INSERT INTO #IPs VALUES('127.0.0.1',NULL)
INSERT INTO #IPs VALUES('192.168.43.192',NULL)
INSERT INTO #IPs VALUES('192.168.1.101',NULL)
INSERT INTO #IPs VALUES('65.54.239.80',NULL)
INSERT INTO #IPs VALUES(NULL,0xB92AEAD3)
INSERT INTO #IPs VALUES(NULL,0x2D4B2E53)
INSERT INTO #IPs VALUES(NULL,0x31031B0B)
INSERT INTO #IPs VALUES(NULL,0x7C2D5F2F)
INSERT INTO #IPs VALUES(NULL,0x473E5D31)
INSERT INTO #IPs VALUES(NULL,0x90D7D66B)
GO
SELECT
	strIP,binIP,
	strIP_new = CAST(CAST(SUBSTRING(binIP,1,1) AS int) AS varchar(3)) + '.' +
				CAST(CAST(SUBSTRING(binIP,2,1) AS int) AS varchar(3)) + '.' +
				CAST(CAST(SUBSTRING(binIP,3,1) AS int) AS varchar(3)) + '.' +
				CAST(CAST(SUBSTRING(binIP,4,1) AS int) AS varchar(3)),
	binIP_new = CAST(CAST(PARSENAME(strIP,4) AS int) AS binary(1)) +
				CAST(CAST(PARSENAME(strIP,3) AS int) AS binary(1)) +
				CAST(CAST(PARSENAME(strIP,2) AS int) AS binary(1)) +
				CAST(CAST(PARSENAME(strIP,1) AS int) AS binary(1)),
	intIP_new = CAST(PARSENAME(strIP,1) AS bigint) +
				CAST(PARSENAME(strIP,2) AS bigint) * 256 +
				CAST(PARSENAME(strIP,3) AS bigint) * 65536 +
				CAST(PARSENAME(strIP,4) AS bigint) * 16777216  --int类型也可以，但浪费空间且不直观
FROM #IPs
</strong>

6.中文字符处理

--ASCII字符
SELECT n,x=CAST(n AS binary(2)),u=NCHAR(n) FROM Nums WHERE n BETWEEN 32 AND 126
--UNICODE中文字符
SELECT n,x=CAST(n AS binary(2)),u=NCHAR(n) FROM Nums WHERE n BETWEEN 19968 AND 40869
19968	0x4E00	一
40869	0x9FA5	龥
--以下两个条件用来判断字符串是否包含汉字
LIKE N'%[吖-咗]%' COLLATE Chinese_PRC_CI_AS
LIKE N'%[一-龥]%' COLLATE Chinese_PRC_BIN
--这是因为在以上两种不同的排序规则下，汉字的排列顺序是不同的。
--中文全角标点符号
SELECT n,x=CAST(n AS binary(2)),uq=NCHAR(n),ub=NCHAR(n-65248) FROM Nums WHERE n BETWEEN 65281 AND 65374
SELECT NCHAR(12288),NCHAR(32)
65281	0xFF01	！	!
65374	0xFF5E	～	~
--以下条件用来判断字符串是否包含全角标点
LIKE N'%[！-～]%' COLLATE Chinese_PRC_BIN

--full2half
CREATE FUNCTION [dbo].[full2half](
@String nvarchar(max)
)
RETURNS nvarchar(max)
AS
/*
全角(Fullwidth)转换为半角(Halfwidth)
*/
BEGIN
	DECLARE @chr nchar(1)
	DECLARE @i int
	SET @String = REPLACE(@String,N'　',N' ')
	SET @i = PATINDEX(N'%[！-～]%' COLLATE Latin1_General_BIN,@String)
	WHILE @i > 0
	BEGIN
		SET @chr = SUBSTRING(@String,@i,1)
		SET @String = REPLACE(@String,@chr,NCHAR(UNICODE(@chr)-65248))
		SET @i = PATINDEX(N'%[！-～]%' COLLATE Latin1_General_BIN,@String)
	END
	RETURN @String
END
GO
CREATE FUNCTION [dbo].[half2full](
@String nvarchar(max)
)
RETURNS nvarchar(max)
AS
/*
半角(Halfwidth)转换为全角(Fullwidth)
*/
BEGIN
	DECLARE @chr nchar(1)
	DECLARE @i int
	SET @String = REPLACE(@String,N' ',N'　')
	SET @i = PATINDEX(N'%[!-~]%' COLLATE Latin1_General_BIN,@String)
	WHILE @i > 0
	BEGIN
		SET @chr = SUBSTRING(@String,@i,1)
		SET @String = REPLACE(@String,@chr,NCHAR(UNICODE(@chr)+65248))
		SET @i = PATINDEX(N'%[!-~]%' COLLATE Latin1_General_BIN,@String)
	END
	RETURN @String
END
GO

7.binary字符串

--string到binary可以用这个系统函数sys.fn_varbintohexstr()（实际上是master.dbo.fn_varbintohexstr）
SELECT sys.fn_varbintohexstr(0x1234),'0x1234'
--binary到string需要自定义函数
CREATE FUNCTION dbo.hexstr2varbin(
@hexstr varchar(max)
)
RETURNS varbinary(max)
AS
/*
将表示16进制的字符串转换为2进制类型
--TESTCASES
SELECT dbo.hexstr2varbin(NULL),NULL
SELECT dbo.hexstr2varbin(''),0x
SELECT dbo.hexstr2varbin('0x'),0x
SELECT dbo.hexstr2varbin('30394161'),0x30394161
SELECT dbo.hexstr2varbin('0x30394161'),0x30394161
SELECT dbo.hexstr2varbin('0x1A2B3C4D5E6F'),0x1A2B3C4D5E6F
SELECT dbo.hexstr2varbin('0x1a2b3c4d5e6f'),0x1a2b3c4d5e6f
--UNIMPLEMENTED
SELECT dbo.hexstr2varbin('0x3039416'),0x3039416
*/
BEGIN
	DECLARE @value int
	DECLARE @ascii int
	DECLARE @varbin varbinary(max)
	IF @hexstr LIKE '0x%'
		SET @hexstr = STUFF(@hexstr,1,2,'')
	SET @hexstr = UPPER(@hexstr)
	IF @hexstr NOT LIKE '%[^0-9A-F]%' COLLATE Chinese_PRC_BIN
	BEGIN
		SET @varbin = 0x
		WHILE @hexstr <> ''
		BEGIN
			SET @value = ASCII(SUBSTRING(@hexstr,1,1))
			IF @value <= 57
				SET @value = @value - 48
			ELSE
				SET @value = @value - 55
			SET @ascii = @value * 16
			SET @value = ASCII(SUBSTRING(@hexstr,2,1))
			IF @value <= 57
				SET @value = @value - 48
			ELSE
				SET @value = @value - 55
			SET @ascii = @ascii + @value
			SET @varbin = @varbin + CAST(@ascii AS binary(1))
			SET @hexstr = STUFF(@hexstr,1,2,'')
		END
	END
	RETURN @varbin
END
GO