SQL查询或带列的视图取决于SELECT查询

Question

My question is maybe silly and will be not so easy to exactly write down. However may example understandable. I am creating a system logging database, which periodically stores values from a hardwer. My tables (in very reduced complexity) are:

VARIABLES table
id_variable    name_variable
1              Temperatur
2              Voltage
...            ...
n              VariableN

LOG_ROWS table
id_log_row     timestamp
1              2012.01.01. 10:00:00
2              2012.01.01. 10:01:00
3              2012.01.01. 10:02:00
n              2012.01.01. 10:0n:00

LOG_VALUES table
id_log_value   id_log_row    id_variable   value
1              1             1             34
2              1             2             1200
3              2             1             35
4              3             1             36
5              3             2             1230

The data structure is important, because I have to add new variables later wothout alter table and each variable has other storing time period. (not all log_rows contains the all variable. Here time period of voltage is 2 min, time period of temperatur is 1 min)

So, I would like to create well readable db view, where the columns are the variable ids or names (here names) joined with log_row's id and timestamp. Something similar to this.

id_log_row    timestamp              Temperatur     Voltage   ...  N
1             2012.01.01. 10:00:00   34             1200           NULL
2             2012.01.01. 10:01:00   35             NULL           NULL
3             2012.01.01. 10:02:00   36             1230      ...  NULL

Is these view possible with SQL? To define columns according to table content. I am interested in. I want to create this in SQLite

Answer 1

SQLite does not support altering a view. It is generally a bad idea to design your data is such a way that you later must alter tables.