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Basic knowledge of day02 MySQL database

1. Overview of basic knowledge:

The foundation determines the success or failure of your course! Only after learning these basic knowledge, can you really use it freely. In order to have a deeper understanding of the database, the road will go farther and farther.

Second, basic knowledge:

1, database (database): the database is like a physical document cabinet, a container, summing up our organized data tables, and so on.

Create database command:

Create database database name

2. View the database

Show databases

3. Open the specified database

Use database name

4. Delete the database

Drop database database name

5. Table: a structured list of data of a particular type, in the form of a grid, to put it bluntly.

Commands for creating tables

Create table table name (field name 1, field name 2,)

6. View table data

Show tables

7. View the table structure

Describe table name; or show columns from table name. Database name

8, column: the concept of column is not unfamiliar to everyone, that is, a vertical data in a grid-type table is called a column.

9. Row: a row is a row of data in a table. The data in the table is stored according to the row, and the saved data is in the row.

10. Primary key (primary key): this is a very important knowledge. As we will say later, a row of data can be uniquely locked when querying data through the primary key. There can be only one primary key in a database table, and it is the only primary key.

11. Modify the table structure

Alter table table name add column definition / add column drop column name / delete column add index index name (column name) / add index drop index index name / / delete index modify column definition Meaning / / modify column definition add primary key (column name) / / add primary key drop primary key / / delete primary key rename new table name / / modify table name

12. Insert data

Insert into table name [(column name,.. n)] values (value,...)

13. View the data in the table

Select column name [as alias] [,... n] | * | expression-> from table name [ . n]-> [where conditional expression]-> [order by column name]-> [group by column name]-> [having conditional expression]-> [like Fuzzy query]-> [concat () Joint Multi-column query]-> [limit qualifies the result row Control the number of rows of output]

14. Delete data from the table

Delete from table name [where conditional expression]

15. Modify data in the table

Update table name set column name = value [where conditional expression]

16. Delete table and duplicate name table

Delete table drop table table name; rename: rename table database name 1 to database name 2

III. Concluding remarks

At this point, I have finished talking about the relevant sql sentences, which may not be comprehensive and detailed enough. I will continue to refine and refine them in later study. Thank you!

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