SQLite Learning note 8:c using SQLite to create tables in the language

I've already said how to open and close the database, this time to say how to execute the SQL statement to create a table.

The function to use:

Sqlite3_exec (sqlite3* db, const char *sql, Sqlite_callback callback, void *data, char **errmsg)

Parameter: DB: An open DB instance Sql:sql statement, is a string callback: is a callback function data: As the first parameter of a callback function ErrMsg: Used to bring back the error message

The callback function has two types of return values.        1. Return 0: Sqlite3_exec () will continue to execute the query.        2. Return non 0: sqlite3_exec () will immediately break the query, and Sqlite3_exec () will return Sqlite_abort.

The callback function is formatted as follows: Int Sqlite_callback (    void* PV,/    * is passed by the fourth parameter of the SQLITE3_EXEC () */    int argc,/        * The number of columns in the table *    / char** argv,    /* Pointer to the query result array, can be obtained by sqlite3_column_text () */    char** col/        * pointer to the table header array, can be sqlite3_column_ Name () (); parameter format:    A callback function passed to sqlite3_exec that displays the query result    called once for each query result:    PV: Initialization parameters passed by sqlite3_exec    argc: Column number of table header    col: Table header array pointer    argv: Data array pointer return value for table header:    1: Interrupt lookup    0: Continue enumerating the data queried

Instance:

 #include < stdio.h> #include <stdlib.h> #include "sqlite/sqlite3.h" #define Db_nane "sqlite/test.db" sqlite3 *db = NULL;  char* sql = Null;char *zerrmsg = null;int ret = 0;typedef enum{false, true} bool;static int callback (void *notused,    int argc, char **argv, char **azcolname) {int i = 0;    for (i=0; i < argc; i++) {printf ("%s =%s\n", Azcolname[i], argv[i]? Argv[i]: "NULL");        } printf ("\ n"); return 0;}        BOOL Connectdb () {ret = Sqlite3_open (Db_nane, &db);        if (ret! = SQLITE_OK) {fprintf (stderr, "Error Open Database:%s\n", sqlite3_errmsg (db));                Sqlite3_free (ZERRMSG);    return false;    } fprintf (stdout, "successfully opened database\n"); return true;} 

/* Added this function relative to the previous article */bool createtable () {/    * Create SQL statement *    /sql = "Create TABLE Company ("      "ID INT PRIMA RY KEY     is not null, "     " NAME TEXT is not    null, "     " age            INT is not     null, "     " ADDRESS        CHAR (50 ), "     SALARY         REAL);";        /* Execute SQL statement *    /ret = sqlite3_exec (db, SQL, callback, 0, &zerrmsg);    if (ret! = SQLITE_OK) {        fprintf (stderr, "Error SQL:%s\n", zerrmsg);        Sqlite3_free (zerrmsg);                return false;    }        fprintf (stdout, "successfully table created\n");        return true;} BOOL Closedb () {    int ret = 0;    ret = sqlite3_close (db);    if (ret = = sqlite_busy) {        return false;    }        return true;} int main (int argc, char* argv[]) {    connectdb ();    CreateTable ();/* Added a function call *    /Closedb ();        return 0;}

This function can only be executed once, the second execution will have an error saying that the table already exists, delete the generated test.db can be executed again.