How to implement SQL statements to obtain database data examples .

1: Create a new database.

create database database name.

2: Create a table.

create table table name.

Whether the field name Type is empty.

3: Delete a table.

drop table name.

4: Add a record.

insert table name [(field)] values (contents)5: Deletes a record.

delete [from] table name where Condition 6, modify a record.

update table name set field name = update content where condition 7, add a field to the original table.

alter table add column field name Type 8: Deletes a field from the original table.

alter table table name drop column field name 9, query a table record.

select * from the table name.

10. Query a table record with conditions.

select * from table name where = condition.

Boss: You're going to solve it, tell me.

insert into testtb01(name) values ('tongqiang')

You're not a kanji either.

Character-based data must be inserted and queried with a pair of English single quotation marks, as I did above.

If you only use it occasionally, it is recommended to use:

select * from

If you use it for a long time, it is good to specify the connection of the program: such as the second floor:

sqlconnection mysql = new sqlconnection("data source=localhost;integrated security=true;initial catalog= database1");

This is a connection connection setting issue and has nothing to do with SQL statements.

sqlconnection mysql = new sqlconnection("data source=localhost;integrated security=true;initial catalog= database1");

MySQL does not support the top syntax, top is the syntax in sqlserver, if you want to check the first piece of data, use it like this.

select * from henweight order by datetime desc limit 0,1

Or select * from henweight order by datetime desc limit 1

MySQL does not support the top syntax, you can use limit

For example, select * from henweight order by datetime desc limit 0,1

I know this question.

It is recommended that you use the "SATH QQ Stranger Promotion Assistant".

You don't need to add friends to send messages directly.

There is absolutely no problem with quoting 10,000 unique IPs per day.

I didn't find a problem, except that the statement should be written in a standard, for example, there is a space in the middle of the from table, and there are spaces before and after, 10pname,pbirthday,cdate,eballs( pcity='Guangzhou'(players balls))) I don't know what that means.

To give you an idea, I don't know what database you are, take sqlserver as an example select t* from

select row number() over (order by time) rn, the name of the table. * from Table Name) t

where rn%30=1

That is, use the line number to remove the remainder, and take out the remainder = 1, so that you can take 1 out of every 30.