PHP study trainer (5)

: This article mainly introduces PHP practitioners (5). If you are interested in the PHP Tutorial, refer to it. Basic exercises for MySQL databases

1. Create a database
   
   
2. Use Database
   
   
3. Create a table
   
   • Char: constant
   • Varchar: variable
     
     
4. Display Table
   
   
5. View table structure
   
   
6. Insert data
   SHA1 (): the data encryption function. it creates an encrypted character and its length is exactly 40 characters.
   
   
7. View all elements
   
   

8. WHERE condition statement
   

9. Between... And...
   
   

10. LIKE/NOT LIKE

    • Wildcard _: match a single character; %: match 0 or multiple characters
    • If '\' is added before the wildcard, '_' or '%' is used only as the original symbol and does not have the wildcard meaning.
    • Queries with the LIKE condition statement are generally slow. because indexes cannot be used, this format should be used only when absolutely needed.

11. Sort order by ascending ASC descending DESC

    • If the column to be sorted is of the ENUM type, the sorting is based on the order in which the ENUM value is created.
      

12. Limit

    • Limit x: returns the first X records in the query record.
    • Limit x, Y: return Y Records starting from X Records
    • The LIMIT clause does not improve the query execution speed, because mysql still has to combine each record and then truncate the list.
      

13. Update, delete
    
    • To prevent accidental updating of too many rows, you can apply a limit clause to update
    • Truncate: truncate table is preferred for clearing a TABLE.Tablename
    • To delete all data in the TABLE and the TABLE itself: DROP TABLETablename;
    • To delete the entire DATABASE: DROP DATABASEDatabasename
      
      
14. Concat connection function
    
    
15. Concat_ws connection function
    
    
16. Length function
    
    
17. Format function
    
    
18. Use concat and format functions
    
    
19. Rand () functions
    
    
20. Now (), curtime (), curdate () functions
    
    
21. Date_format function
    

'). AddClass ('pre-numbering '). hide (); $ (this ). addClass ('Has-numbering '). parent (). append ($ numbering); for (I = 1; I <= lines; I ++) {$ numbering. append ($ ('

'). Text (I) ;}; $ numbering. fadeIn (1700) ;}) ;}; script

The above introduces PHP learning and practice (5), including some content, and hopes to help those who are interested in PHP tutorials.