• SQL wildcard


    SQL wildcard SQL wildcards can replace one or more characters when searching for data in a database. The SQL wildcard must be used with the like operator. In SQL, you can use the following wildcards: wildcard describe % Replace one or more characters _ Replace only one character [charlist] Any single character in a character […]

  • First acquaintance with MySQL


    Data storage architecture Database server runs database management system (DBMS), database management system (database), database organization table (table), table storage record Common databases Relational (RDBMS):Table structure is used to store data. Each data must have the same structure MySQL: the most extensive Oracle: used by finance and state-owned enterprises SQL Server: teaching use Sqllite: lightweight, […]

  • C language package, unpack and browse package file information based on form command line


    #include#include#include#include#include#include#include using namespace std; int count=0;  typedef struct Note{  char path[50];  struct Note *next; }Note,*Lnote;  typedef struct Node {  char name[20];  unsigned int size;   struct Node *next;     }Node,*List;  List creat(void); void add(List *head,char *Tname,int Tsize); void bwrite(char *fn);  void file_in(char *Path_r,char *Path_w); void unzip(char *Path_file,char *Path_out); void lookthepack(char *path); Lnote Tcreat(void); void Tadd(Lnote *Thead,char *Path); void zip(char *ar1,char *ar2);     void lookthepack(char *path){  int i,j;  Node p;  FILE *fp;   if((fp=fopen(path,”rb”))==NULL){   printf(“Can’t open %s\n”,path);    exit(1);   }   fseek(fp,0L,SEEK_SET);    rewind(fp);   fread(&j,sizeof(j),1,fp);Printf (“the total number […]

  • What is the difference between set and set in Java?


    As you may know, the unbounded wildcard set > can hold any type of element, and the original type set can hold any type of element. What’s the difference between them? 1. Two facts about set > There are two facts about set > Item 1:? Represents any type. Set > can hold any type […]

  • Detailed explanation and examples of wildcards in Linux


    Detailed explanation and examples of wildcards in Linux A wildcard Two actual combat [[email protected] ~]# mkdir dy [[email protected] ~]# cd dy [[email protected]st dy]# touch dzp dzp2 dzp3 dzp34 dzpcang dzpbols [[email protected] dy]# ls dzp dzp2 dzp3 dzp34 dzpbols dzpcang [[email protected] dy]# la dzp bash: la: command not found… [[email protected] dy]# ls dzp dzp [[email protected] dy]# […]

  • MySQL Filtration (Geek Time Learning Notes)


    Data filtering Data filtering in SQL can reduce unnecessary data rows and improve query efficiency. Comparison operator In SQL, it is very important to use WHERE clause to filter conditions and compare operators when filtering. The comparison operator above does not mean that every DBMS supports MySQL, but does not support (!>) and (!<) etc. […]

  • Introduction of wildcards and operators in Oracle


    The conditions for where comparison are: Equivalent to: =,<,<=,>>=,<> Contains: in, not in exists, not exists Scope: between and, not between. Matching test: like, not like Null test: is null, is not null Boolean links: and, or, not  Wildcard: In the where clause, wildcards can be used with like conditions. In Oracle: Percentage sign: Used […]

  • Common commands in composer


      Some commonly used composer commands: # Display all installed packages composer show # Remove the specified dependency package_name composer remove package_name # Search for information with package_name composer search package_name # Add a specified package (no need to manually add dependency information in composer. json) # Compooser finds the appropriate version, updates the composer. […]

  • Detailed description of upper bound and lower bound wildcards on Java generics


    Generics, Inheritance and Subclasses As you know, as long as the type is compatible, one type of object can be assigned to another type of object. For example, you can specify an integer as an object because the object is a supertype of an integer: Object someObject = new Object(); Integer someInteger = new Integer(10); […]

  • Wildcards and regular expressions under Linux


    wildcard * Any character can be repeated many timesAny character, repeat it[] Represents a character Examples: [a, b, c] denotes any one of the ABCs Wildcards are used to match file names regular expression Regular expressions match qualified strings in a file Ls find CP does not support regular expressions But grep awk sed supports […]

  • Fuzzy Query in Oracle SQL Language–A detailed tutorial on the use of wildcard like


    In the Where clause, Oracle can use the Like clause with wildcards to select data records that are “very similar to…” for columns of field types of datetime, char and varchar. The following wildcards are available: % Zero or more characters _ Single any character (underscore) \ Special Characters Oracle 10g or more supports regular […]