iOS 数据库表添加字段

在iOS中新版本更新涉及字段改动时有发生，为保留原有数据完成数据更新，可以采用一下代码

• (void)alterItemTableToAddFilterColumnsIfNeeded {

[self alterItemTableToAddFilterColunm:@"Color"];

[self alterItemTableToAddFilterColunm:@"FashionStyle"];

[self alterItemTableToAddFilterColunm:@"Category"];

}

• (void)alterItemTableToAddFilterColunm:(NSString *)columnName {

//没有添加该列则修改添加

if (![self checkFilterColumnExists:columnName]) {

[self alterItemTableToAddColumn:columnName];

}

}

• (BOOL)checkFilterColumnExists:(NSString *)columnName {

__block BOOL returnBool = NO;

[_queue inDatabase:^(FMDatabase *db) {

[db open];

FMResultSet *resultSet = [db executeQuery:[NSString stringWithFormat:@"PRAGMA table_info(%@)", @"Item"]];

NSMutableArray* columnNames = [[NSMutableArray alloc] init];

while ([resultSet next]) {

if ([[resultSet stringForColumn:@"name"] isEqualToString: columnName]) {

returnBool = YES;

break;

}

}

[db close];

}];

return returnBool;

}

• (void)alterItemTableToAddColumn:(NSString *)columnName {

NSString *alterSql = [NSString stringWithFormat:@"ALTER TABLE Item ADD COLUMN %@ TEXT DEFAULT ''", columnName, nil];

[_queue inDatabase:^(FMDatabase *db) {

[db open];

if ([db executeUpdate:alterSql]) {

NSLog(@"Alter Item Filter Success!");

} else {

NSLog(@"Alter Item Filter Error!");

}

[db close];

}];
}