mirror of
https://github.com/koreader/koreader
synced 2024-11-13 19:11:25 +00:00
71 lines
2.0 KiB
Markdown
71 lines
2.0 KiB
Markdown
Data Store
|
|
==========
|
|
|
|
## LuaSettings ##
|
|
|
|
TODO
|
|
|
|
|
|
## DocSettings ##
|
|
|
|
TODO
|
|
|
|
|
|
## SQLite3 ##
|
|
|
|
KOReader ships with the SQLite3 library, which is a great embedded database for
|
|
desktop and mobile applications.
|
|
|
|
[lua-ljsqlite3][ljsq3] is used to export SQLite3 C interfaces as LUA functions.
|
|
Following is a quick example:
|
|
|
|
```lua
|
|
local SQ3 = require("lua-ljsqlite3/init")
|
|
|
|
local conn = SQ3.open("/path/to/database.sqlite3")
|
|
|
|
-- Execute SQL commands separated by the ';' character:
|
|
conn:exec([[
|
|
-- time is in unit of seconds
|
|
CREATE TABLE IF NOT EXISTS page_read_time(page INTEGER, time INTEGER);
|
|
CREATE TABLE IF NOT EXISTS book_property(title TEXT, author TEXT, language TEXT);
|
|
]])
|
|
|
|
-- Prepared statements are supported, with this you can bind different values
|
|
-- to the same statement. Let's set the read time for the first 10 pages in the
|
|
-- book to 5 seconds
|
|
local stmt = conn:prepare("INSERT INTO page_read_time VALUES(?, ?)")
|
|
for i=1,10 do
|
|
stmt:reset():bind(i, 5):step()
|
|
end
|
|
|
|
-- Now we can retrieve all read time stats for the first 10 pages:
|
|
local results = conn:exec("SELECT * FROM page_read_time") -- Records are by column.
|
|
-- Access to results via column numbers or names:
|
|
assert(results[1] == results.page)
|
|
assert(results[2] == results.time)
|
|
-- Nested indexing corresponds to the record(row) number, access value for 4th page:
|
|
assert(results[1][4] == 4)
|
|
assert(results[2][4] == 5)
|
|
-- access value for 2nd page:
|
|
assert(results.page[2] == 2)
|
|
assert(results.time[2] == 5)
|
|
|
|
-- Convenience function returns multiple values for one record:
|
|
local page, time = conn:rowexec("SELECT * FROM page_read_time WHERE page==3")
|
|
print(page, time) --> 3 5
|
|
|
|
-- We can also use builtin aggregate functions to do simple analytic task
|
|
local total_time = conn:rowexec("SELECT SUM(time) FROM page_read_time")
|
|
print(total_time) --> 50
|
|
|
|
conn:close() -- Do not forget to close stmt after you are done
|
|
```
|
|
|
|
For more information on supported SQL quries, check out [SQLite3's official
|
|
documentation][sq3-doc].
|
|
|
|
|
|
[ljsq3]:http://scilua.org/ljsqlite3.html
|
|
[sq3-doc]:https://www.sqlite.org/docs.html
|