Basic syntax of VB

Imports System

Module Program
    Sub Main(args As String())

        Dim a, b As Int32
        a = 1
        b = 2

        If a < 1 Then
            Console.WriteLine(" result 1")
        Else
            Console.WriteLine(" result 2")
        End If

        Console.WriteLine("========================")

        For index = 1 To 10
            Console.WriteLine(index)
        Next

        If True Then

        End If

        Console.WriteLine("Hello World!")

        Dim c(3) As Integer

        c(1) = 1
        c(2) = 1
        c(3) = 3

        For index = 1 To 3
            Console.WriteLine(c(index))
        Next

        Console.WriteLine("==========For Each========================")

        For Each item In func1()
            Console.WriteLine(item)
        Next

        Console.WriteLine("==========Sub function ========================")
        func2()

        //Public integerClass As New classHolder(Of Integer)

    End Sub



    Public Function func1() As Integer()
        Dim a(10) As Integer

        For index = 1 To 10
            a.Append(index)
        Next
        func1 = a
    End Function

    Public Sub func2()
        Console.WriteLine(“ This is a func2()”)
    End Sub


    Public Class Customer
        Public Sub New()
            Debug.WriteLine("setuped")

        End Sub

        '--------New(Byval)---------
        Public Sub New(ByVal sname As String)
            Name = sname
            Debug.WriteLine(Name & "setuped")
        End Sub

        Private m_Name As String
        Property Name() As String
            Get
                Return m_Name
            End Get
            Set(ByVal Value As String)
                m_Name = Value
            End Set
        End Property
        Private m_address As String
        Property Address() As String
            Get
                Return m_address
            End Get
            Set(ByVal Value As String)
                m_address = Value
            End Set
        End Property

        Public Function PlaceOrder() As String

        End Function

        Public Function CheckOrderStatus() As String

        End Function

        Public Overridable Function CalculateDiscount() As String
            Return "base class"
        End Function
    End Class

    Public Class SubPro : Inherits Customer

        Private m_zfjg As String
        Property Zfjg() As String
            Get
                Return Zfjg
            End Get
            Set(ByVal Value As String)
                m_zfjg = Value
            End Set
        End Property

        Private m_bsc As String
        Property Bsc() As String
            Get
                Return m_bsc
            End Get
            Set(ByVal Value As String)
                m_bsc = Value
            End Set
        End Property

        Public Overrides Function CalculateDiscount() As String
            Return "sub class"
        End Function
        Public Function SubProSelf() As String

        End Function
        Public Sub New()
            MyBase.New()
        End Sub
    End Class

End Module

result ：

result 2

1
2
3
4
5
6
7
8
9
10
Hello World!
1
1
3
For Each==============
0
0
0
0
0
0
0
0
0
0
0
Sub function ==============
This is a func2()

D:\Csharp\VBTest\VBTest\bin\Debug\net6.0\VBTest.exe ( process 1600) Exited , The code is 0.
To automatically close the console when debugging stops , Please enable “ Tools ”->“ Options ”->“ debugging ”->“ Automatically close the console when debugging stops ”.
Press any key to close this window . . .

 One 、 Insert statement 
1.  Normal insert 
insert into tableA( Field 1, Field 2, Field 3)values( field value 1, field value 2, field value 3)
 example ：

insert into tableA(
	userName,
	userSex,
	userPhone
)values(
	' Zhang San ',
	' male ',
	'18812345678'
)

2.  Table data query ( Copy ) Insert 
insert into tableA( Field 1, Field 2, Field 3)select ( Field 4, Field 5, Field 6) from tableB

insert into tableA(
	userName,
	userSex,
	userPhone
)select
	memberName,
	memberSex,
	memberPhone
 from tableB
 where ……

 Two 、 Query statement 
1.  All data queries 
select  Field 1, Field 2, Field 3 from tableA where ……
 example ：

select
	userName,
	userSex,
	userPhone
from tableA
where ……

2.  How many pieces of data before query according to a certain condition 
select top n  Field 1, Field 2, Field 3 from tableA where ……
(n Is the number of data pieces )
 example ( front 10 Data )：

select
	top 10
	userName,
	userSex,
	userPhone
from tableA
where ……
order by userName

 3、 ... and 、 UPDATE statement 
1.  Single table data update 
update tableA set  Field 1=‘ field value 1’, Field 2=‘ field value 2’, Field 3=‘ field value 3’ where……
 example ：

update tableA
set userName=' Li Si ',
userSex=' male ',
userPhone='13012345678'
where userName=' Zhang San '

2.  Multi table joint data update 
update a set a. Field 1=b. Field 4,a. Field 2=b. Field 5,a. Field 3=b. Field 6
from tableA a left join tableB b on a.userId=b.userId
where……
 example ：

update a
set a.userName=b.userName,
a.userSex=b.userSex,
a.userPhone=b.userPhone
from tableA a 
left join tableB on a.userId=b.userId
where ……

 Four 、 Delete statements 
delete from tableA where ……
 example ：

delete from tableA where userName=' Zhang San '
1
 5、 ... and 、case when……else
case when  Conditions 1 then ……when  Conditions 2 then……else……end
 example ：

select
	case when sexFlag=0 then ' Woman '
	when sexFlag=1 then ' male '
	else ' Unrecognized '
	end userSex
from tableA

 6、 ... and 、left join( Left Association query )
 The result set returns the left table (tableA) All the data , If the left table exists 、 Right table (tableB) If there is no data, the data in the right table will return null
 example ：

select
	a.userName,--tableA Name of the person in the table 
	b.userOrderId--tableB Order No. of Chinese personnel , If not, return null
from tableA a
left join tableB b on a.userId=b.userId

 7、 ... and 、right join( Right association query )
 The result set returns the right table (tableB) All the data , If the right table exists 、 The left table (tableA) If there is no data, the data in the left table will return null
 example ：

select
	a.userName,--tableA Name of the person in the table , If not, return null
	b.userOrderId--tableB All order numbers in 
from tableA a
right join tableB b on a.userId=b.userId

 8、 ... and 、inner join( Internal association query )
 The result set returns the left table (tableA) And the right watch (tableB) All existing data 
 example ：

select
	a.userName,--tableA Name of the person in the table 
	b.userOrderId--tableB All order numbers in 
from tableA a
inner join tableB b on a.userId=b.userId

 Nine 、like
 Fuzzy conditional query , Query the result set of a field value containing a string 
 example ( The query name contains 【 countries 】 All personnel information of the word )：

select
……
from tableA
where userName like '% countries %'

 Ten 、concat
 Character replacement and splicing combination 
 example ( full name / Gender / The mobile phone number is combined into one field )：

select
-- return ： Zhang San - male -18812345678
CONCAT(userName,'-',userSex,'-',userPhone) as userInfo
from tableA
where ……

 11、 ... and 、charindex
 Determine whether a field value contains a string , If yes, the position of the string is returned ( Greater than 0), If not, return 0, It is generally used for filtering conditions 
 example ( The query name contains 【 countries 】 All personnel information of the word )：

select
……
from tableA
where charindex(' countries ',userName)>0
1
2
3
4
 Twelve 、substring
 Intercepting string 
 example ：

select
-- Mobile number No 4 Bit start to intercept , Co interception 4 position 
substring(userPhone,4,4)
from tableA


 One 、 database 

1  Modify the database name & Delete database 
alter database tablename_old modify name = tablename_new;

drop database tablename;

 Two 、 Data type recognition 

2.1  Numeric type 

 

2.2  The date type 

 

2.3  String type 

 

 3、 ... and 、 Modify the order ——alter

3.1  Modify field type 

alter table tableA alter column name varchar(10);

alter table tableA alter column age float not null;

3.1  newly added & Delete primary key 

alter table tableA add constraint KID( Primary key constraint name )  primary key(ID);

alter table tableA drop constraint KID;

3.1  change & Add field name 

exec sp_rename 'tableA .age','userage','column';

alter table tableA add grade varchar(10) not null;

 Four 、 Primary key & Foreign keys （ A little ）

 5、 ... and 、 Insert new record ——insert

5.1  Insert new row 

insert into tableA ('column1','column2','column3','column4') values ('value1','value2','value3','value4'),('value1','value2','value3','value4'),...('value1','value2','value3','value4');

insert into tableA ('column1','column2','column3','column4')  select column1,column2,column3,column4 from tableB ;

 6、 ... and 、 Modify the record ——updata

6.1 updata tableA set   Field  =  value   where   Field = value （ Limiting conditions ）

  7、 ... and 、 Delete record ——delete

7.1 delete from  tableA where  Field = value （ Limiting conditions ）

 8、 ... and 、 Conditionality ——where

8.1  Exact conditions 

where  Field  = ' value '

8.2  Fuzzy conditions 

where  Field   like '% value %'

 Nine 、between&not between grammar 

select * from tableA where ID between 10 and 20;

select * from tableA where ID  not  between 10 and 20;

 Ten 、 Subquery in&not in grammar 

select * from tableA where name in  ('zhangsan',''lisi) ;

select * from tableA where name not  in  ('zhangsan',''lisi);

select * from tableA where name   in  (select  name  from tableB );

select * from tableA where name  not  in  (select  name  from tableB );

 11、 ... and 、 Return the result sort ——order by

select * from  tableA  order by ID desc; # according to ID Descending 

select * from  tableA  order by ID asc ;# according to ID Ascending 

select * from  tableA  order by ID asc ,age desc ;# First according to ID Ascending , And then ID On the basis of ascending order age Descending ;

 Twelve 、  Relational query 

12.1 inner join—— Internal connection 

select * from tableA inner join tableB on tableA.ID = tableB.ID;

12.2 left join—— Left connection 

select * from tableA left join tableB on tableA.ID = tableB.ID;

12.3 right join—— The right connection 

select * from tableA right join tableB on tableA.ID = tableB.ID;

12.4 full join—— Full connection 

select * from tableA full join tableB on tableA.ID = tableB.ID;

 Twelve 、  function 

12.1  Returns the number of characters in a string ——len()

12.2  Return current time ——getdate()、getutcdata()

12.3  Convert date format ——convert(datetype,date_to_be_converted,style)







convert(verchar(10),getdate(),110)

12.4  Calculate the time difference ——datediff(datepart,startdate,enddate)

#datepart Constant value ：day,month,year,hour,minute

select datediff(day,'2020-05-01','2020-05-03') ; # result 2

select datediff(month,'2020-05-01','2020-06-03') ; # result 1

12.5  Add dates ——dateadd(datepart,number,date)

select dateadd(day,3,'2020-05-01') ; # result 2020-05-04

select dateadd(day,-3,'2020-05-01') ; # result 2020-04-28

12.6  Get a separate part of the date ——datepart(datepart,number,date)

select datepart(day,getdate());#select datepart(dd,getdate()); The return type is int integer 

select datename(day,getdate());#select datename(dd,getdate()); The return type is varchar type 

select day(getdate();select month(getdate();select year(getdate();

12.7  Returns the position of a character in another string ——charindex()、patindex()



select charindex('cc','aabbccdd');# Return results 5;

select patindex('%dd','aabbccdd');# Return results 7(%dd: Whether or not to dd ending );

12.8  Delete & Replace the specified length of characters ——stuff( character string , Starting position , length , Alternative string )

select stuff('aabbccdd',5,2,'ee');# Return results aabbeedd;

12.9  Intercepts a string of specified length ——substring( character string , Starting position , length )

select substring('aabbccdd',5,2);# Return results cc;

12.10  Intercepting string ——left()、right()

select left('aabbccdd',5);# Return results aabbc;

select right('aabbccdd',5);# Return results bccdd;

12.10  Divide the string by spaces ——ltrim()、rtrim()



select ltrim(' aabbccdd ');# Return results 'aabbccdd ';

select rtrim(' aabbccdd ');# Return results ' aabbccdd ';

12.11  String case conversion ——lower()、upper()

select lower('Abc');# Return results abc

select upper('Abc');# Return results ABC

12.12  String substitution ——replace()

select replace('aabbccddcc','cc','ee');# Return results aabbeeddee;

12.13  Duplicate string ——replicate() 、space()

select replicate('aab',3);# Return results aabaabaab;

select 'a'+space(5)+'a';# Return results 'a a';

12.14  Invert string position ——reverse()

 select reverse('aab');# Return results baa;

12.15  Change field type ——cast()

 select cast(123 as varchar(10));# Integer to character ;

 select cast(12.5 as decimal(18,2));# Return results 12.50;

12.16  Conditional judgment conversion function ——case()

select case when sex='1' then ' Woman ' else ' male ' end as sex from tableA;