如果既不想寫回調(diào)函數(shù)，又想避免sqlite3_get_table之后麻煩的一維數(shù)組遍歷，那么利用sqlite3_prepare_v2執(zhí)行sql select語句，讓后sqlite3_step遍歷select執(zhí)行的返回結(jié)果是一個非常方便的solution. 當(dāng)然，你必須要明白sqlite3_prepare_v2不僅僅能夠執(zhí)行table的query selection，也能方便地進(jìn)行sql Delete, Insert, Update等其他一些操作。它能幫你把sql語句的執(zhí)行操作變的更加優(yōu)雅。

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int?sqlite3_prepare_v2(??

??sqlite3?*db,????????????<span?style="color:#009900;">/*?Database?handle?*/</span>??

??const?char?*zSql,???????<span?style="color:#009900;">/*?SQL?statement,?UTF-8?encoded?*/</span>??

??int?nByte,??????????????<span?style="color:#009900;">/*?Maximum?length?of?zSql?in?bytes.?*/</span>??

??sqlite3_stmt?**ppStmt,??<span?style="color:#009900;">/*?OUT:?Statement?handle?*/</span>??

??const?char?**pzTail?????<span?style="color:#009900;">/*?OUT:?Pointer?to?unused?portion?of?zSql?*/</span>??

);??

[cpp]?view plaincopy

int?sqlite3_step(sqlite3_stmt*);??

下面以一段iOS中的selection查詢?yōu)槔f明二者的用法：

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-(void)InitializeFilesTable??

{??

????const?char?*?query?=?"SELECT?*?FROM?[FileObjects]";??

????sqlite3_stmt?*?stmt;??

????int?result?=?sqlite3_prepare_v2(mDatabase,?query,?-1,?&stmt,?NULL);??

????if(SQLITE_OK?!=?result)??

????{??

????????sqlite3_finalize(stmt);??

????????<span?style="color:#009900;">//?The?table?has?not?been?created.?Most?likely,?this?is?the?first?time?we?create?the?database.??

????????//?Therefore,?create?all?tables?in?it</span>??

????????char?*?sql?=?"Create?TABLE?[FileObjects]?([FileId]?VARCHAR(128),[FileExt]?VARCHAR(128),?[FileName]?VARCHAR(128),?[FileUrl]?VARCHAR(128),?[FileType]?INT??);";?<span?style="color:#009900;">//?NOXLATE</span>??

????????char?*?errMsg;??

????????result?=?sqlite3_exec(mDatabase,?sql,?NULL,?NULL,?&errMsg);??

????}??

????else??

????{??

????????<span?style="color:#009900;">//?Select?returns?OK,?initialize?the?memory?model?from?the?result</span>??

????????NSMutableDictionary?*?files?=?[NSMutableDictionary?new];??

????????while(sqlite3_step(stmt)?==?SQLITE_ROW)??

????????{??

????????????FileObject?*?file?=?[FileObject?new];??

??????????????

????????????const?char?*?str?=?(const?char?*)sqlite3_column_text(stmt,?0);??

????????????file.FileId?=?str??[[NSString?alloc]?initWithUTF8String:str]?:?@"";??

??????????????

????????????str?=?(const?char?*)sqlite3_column_text(stmt,?1);??

????????????file.FileExt?=?str??[[NSString?alloc]?initWithUTF8String:str]?:?@"";??

??????????????

????????????str?=?(const?char?*)sqlite3_column_text(stmt,?2);??

????????????file.FileName?=?str??[[NSString?alloc]?initWithUTF8String:str]?:?@"";??

??????????????

????????????str?=?(const?char?*)sqlite3_column_text(stmt,?3);??

????????????file.FileUrl?=?str??[[NSString?alloc]?initWithUTF8String:str]?:?@"";??

??????????????

????????????file.FileType?=?sqlite3_column_int(stmt,?4);??

??????????????

????????????[files?setObject:file?forKey:file.FileId];??

????????}??

??????????

????????sqlite3_finalize(stmt);??

????????[mFiles?setDictionary:files];??

????}??

}??

這其中包括對sqlite3_exec的調(diào)用。sqlite3_exec可以執(zhí)行任何sql語句，包括事務(wù)("BEGIN TRANSACTION")、回滾("ROLLBACK")和提交("COMMIT")等等。

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