IOS growth path-database data addition and query

/* =--= Add data to the sqlite3 database ===--= * // 1. define a sqlite3 pointer sqlite3 * dB; // 2. the return value int dbrc for receiving successful read/write database operations; // 3. const char * dbfilepathutf8 = [dbfilepath utf8string]; // 4. open the database dbrc = sqlite3_open (dbfilepathutf8, & dB); // determine whether the IF (dbrc = sqlite_ OK) {nslog (@ "");} // 5. define the SQL statement execution pointer sqlite3_stmt * DBPs; // 6. define the SQL statement nsstring * insertstatementns = [nsstring s Tringwithformat: @ "insert into \" Shopping \ "\ (item, price, groupid, dateadd) \ values (\" % @ \ ", % @, % d, datetime ('now ') ", @" lll ", @" 350 ", 2]; // 7. convert the SQL statement of the defined nsstring to the C-style string const char * insertstatement = [insertstatementns utf8string] of utf8; // 8. SQL statement pre-execution. (Determine whether the SQL statement meets the syntax) dbrc = sqlite3_prepare_v2 (dB, insertstatement,-1, & DBPs, null); // 9. execute the SQL statement dbrc = sqlite3_step (DBPs); nslog (@ "dbrc = % d", dbrc ); /* =--= read data in the database =--= * // 1. define a query statement nsstring * querystatementns = @ "select key, item, price, groupid, dateadd from shopping"; // 2. convert the defined nsstring query statement to the utf8 C string const char * querystatement = [querystatementns utf8string]; // 3. SQL statement preprocessing dbrc = sqlite3_prepare_v2 (dB, querystatement,-1, & DBPs, null); nslog (@ "prepared statement = % d", dbrc); // 4. obtain the value. Use a matched method to obtain the value of the corresponding type and convert the while (dbrc = sqlite3_step (DBPs) = sqlite_row) type) {// obtain the primary key value. For int type, use the optional int primarykeyvaluei = sqlite3_column_int (DBPs, 0); // convert the value to nsnumber * primarykeyvalue = [[nsnumber alloc] initwithint: primarykeyvaluei]; nslog (@ "primarykeyvalue = % @", primarykeyvalue); // use sqlite3_column_text nsstring * itemvalue = [[nsstring alloc] initwithuf8string: (char *) sqlite3_column_text (DBPs, 1)]; nslog (@ "itemvalue = % @", itemvalue); // for the double type of price value, use repeated pricevalued = sqlite3_column_double (DBPs, 2 ); nslog (@ "pricevalued = % lf", pricevalued); // Conversion Type nsnumber * pricevalue = [[nsnumber alloc] initwithdouble: pricevalued]; nslog (@ "pricevalue = % @", pricevalue); // obtain the guoupid value int groupvaluei = sqlite3_column_int (DBPs, 3); nslog (@ "groupvaluei = % d ", groupvaluei); nsnumber * groupvalue = [[nsnumber alloc] initwithint: groupvaluei]; nslog (@ "groupvalue = % @", groupvalue ); // obtain the dateadd value nsstring * datevalues = [[nsstring alloc] initwithuf8string :( char *) sqlite3_column_text (DBPs, 4)]; nslog (@ "datevalues = % @", datevalues);} // 10. release sqlite3_finalize (DBPs); // 11. close the database sqlite3_close (db );