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Anonymous users2024-02-0641.where statement.
42.drop statement: drop table s
43.alter statement: alter table table1 add(columnname, varchar(32)).
44.insert statement: insert into s values('Zhang Er','Chemistry',80)
45. drop view viewname
46. sname(in s) -cname(in c)
48. where = 'Male' and = "Databases"
49.update statement: update s set grade = 85 where sn ="Wang II" and cn = "Chemistry"
50.insert statement: insert into s values('Zhang Er','Chemistry',80)
51.alter statement: alter table table1 add(cn, varchar(32).
52.The number of rows that meet the requirements is counted.
54.Second Paradigm.
55.Department number.
56.First Paradigm.
57.Third Paradigm.
58.Completely dependent on either one.
59.First Paradigm.
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Anonymous users2024-02-05The length of the bytes that you can only recognize is 8 bytes, and since you don't have anything to store, you can't see the remaining storage space.
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Anonymous users2024-02-04char(8) is 8 bytes, each byte holds one letter, then abc occupies three bytes, then the rest is 5 bytes.
Because varchar(8) is a variable length, the length occupied by abc is the entire length, so varchar has no space left. It's 3 bytes + 1 byte (this byte is the length byte (sometimes this byte is not counted because this byte is not within 8)).
nvarchar(8) is a variable Unicode character. Each character in nvarchar is a Unicode character, so each character occupies two bytes, which means that it occupies 6 bytes, and the remaining space is 0
nchar(8) is basically the same as nvarchar(8), it is also a unicode character, but it is not mutable, so it still occupies 6 bytes, and the remaining space is 16-6=10 bytes.
Create a database.
Select the Program Management SQL Server 2008 SQL Server Management Studio command in the Start menu to open the SQL Server Management Studio window and establish a connection using Windows or SQL Server authentication. >>>More
The database is generally composed of many tables, for example, the school builds a database, which can build a student table (including the student's name, age, student number, class, date of birth), a teacher table (including the teacher's name, age, teaching class, teaching category), a report sheet (including the student's student number, and the grades of each subject), etc. These are the ways in which the files are stored in the database, and try to make sure that the items in a table are closely related and have the same attributes, if this condition cannot be met, a table must be built (the redundancy of the built table has 4 levels). In order to meet the user's query needs, we also need to make a number of views, for example, you can make a view of his items have the name of the student, age, grades of each subject, and the teacher of each subject, etc., we can also export new items according to the existing items, for the purpose of simplicity, for example, the view can add an average grade, we add different permissions and roles to each view, and provide it to different people to query to protect the security of the database. >>>More
select ,from emp e left jion dept don ;
Left Company. The left link is, the left side prevails, and the right side is useless to make up for it. >>>More
There is no bottom in select
select top 1 * from table order by field 1 desc" >>>More
It seems that there is something called triggers in the DB, and there seems to be another thing called transactions.