SQLite, sqlite3

SQLite, sqlite3
What is SQLiteSQLite? It is a lightweight embedded database, which occupies very low resources. In embedded devices, it may only require several hundred KB of memory, which is faster than Mysql and PostgreSQL. What is Database) A warehouse database that organizes, stores, and manages data according to the data structure can be divided into two types: relational databases (mainstream) common relational databases of object type databases PC end: oracle, MySQL, SQL Server, Access, DB2, Sybase embedded \ mobile client: the storage structure of a database that stores data in SQLite databases is similar to that in excel) create a table by adding multiple fields (column, column, and attribute)

 

Data Storage Method for adding multi-row records (row stores values of multiple fields in each row): Plist (NSArray \ NSDictionary) Preference (Preference setting \ NSUserDefaults) NSCoding (NSKeyedArchiver \ NSkeyedUnarchiver) SQLite3Core Data

1. Open the database

Int sqlite3_open (

Const char * filename, // path of the database file

Sqlite3 ** ppDb // database instance

);

 

2. execute any SQL statement

Int sqlite3_exec (

Sqlite3 *, // an open database instance

Const char * SQL, // SQL statement to be executed

Int (* callback) (void *, int, char **, char **), // callback after the SQL statement is executed

Void *, // The 1st parameters of the callback function

Char ** errmsg // error message

);

 

3. Check the validity of SQL statements (preparations before query)

Int sqlite3_prepare_v2 (

Sqlite3 * db, // database instance

Const char * zSql, // SQL statement to be checked

Int nByte, // the maximum length of the SQL statement in bytes

Sqlite3_stmt ** ppStmt, // sqlite3_stmt instance for obtaining database data

Const char ** pzTail

);

 

4. query a row of data

Int sqlite3_step (sqlite3_stmt *); // If a row of data is queried, SQLITE_ROW is returned.

 

5. Use stmt to obtain the value of a field (the subscript of the field starts from 0)

Double sqlite3_column_double (sqlite3_stmt *, int iCol); // floating point data

Int sqlite3_column_int (sqlite3_stmt *, int iCol); // Integer Data

Sqlite3_int64 sqlite3_column_int64 (sqlite3_stmt *, int iCol); // long integer data

Const void * sqlite3_column_blob (sqlite3_stmt *, int iCol); // binary text data

Const unsigned char * sqlite3_column_text (sqlite3_stmt *, int iCol); // string data