day80

1: Fuzzy query:

  Select*from book where name like ‘java%’or type like ‘java%’)and (price <50)and (price>30);

Invalid column type: The database has null values ​​when passing values;

2: If the database is locked, enter the statement: " /as sysdba "    show user conn ccms/ccms ;

3 : Types of fields in the database:

   A:primary key (field): primary key

   B:unique key (field): unique constraint

   C:constrint DF_field dafault ( "default value") for field: default constraint

   D:constrint CK_field check (constraint , such as: len (field) > 1 ),

   E : constriant FK_main table_slave table foreign ( foreign key field) reference main table (primary table primary key field) 

Struts2 framework:

 The environment is configured