SQL Result Type

[StemonZhang]

I am confused , what's the type of the SQL Result?

I used the Lua get the data stored in MySQL DB .

The SQL statement is db:query("select result from result_table order by data_time desc limit 1").

I want to get the result. But I don't know the type of it~

when I use like this:

                    if table.getn(res) ~= 0 then
                            ngx.say(res[1][1]) ;
                    end

The result is nil. But I directly used the same SQL Statement to the MySQL DB, it could get the result I wanted.

When I use like this:

                    if table.getn(res) ~= 0 then
                            ngx.say(res[1]) ;
                    end

It threw error: runtime error: [string "rewrite_by_lua"]:39: bad argument #1 to 'say' (non-array table found)

It's strange, I search the Internet ,but there is no answer about the type of the SQL Result.

THX~

[agentzh]

Which MySQL client are you using? Are you using the lua-resty-mysql library? If yes, you should consult its documentation for details on the output results. Basically, it is documented in the read_query method's documentation:

https://github.com/agentzh/lua-resty-mysql#read_result

That is, by default, you should access a single field in the form res[row_num][column_name], for instance,

res[1]["id"]

accesses the "id" field in the 1st row of the resultset.

But also be aware of the "compact_arrays" option in the "connect" method:

https://github.com/agentzh/lua-resty-mysql#connect

Regards,
-agentzh

[StemonZhang]

It did work.res[row_num][column_name]is OK.
I thought it was res[row_num][column_num] before.
So it worked wrong.
I checked the info in https://github.com/agentzh/lua-resty-mysql#connect.
But It did not do this definitely.
Just use these words to describe the info like this:

It returns a Lua table (res) describing the MySQL OK packet or result set packet for the query result.

For queries corresponding to a result set, it returns an array holding all the rows. Each row holds key-value apirs for each data fields.

But now I think it already do the job, because it said : "Each row holdskey-valueapirs for each data fields".

Key-Value is the most info, but I ignored it , it's my fault.

Thank you very much, Big Zhang^_^

At 2013-08-30 23:46:37,"Yichun Zhang" [email protected] wrote:

Which MySQL client are you using? Are you using the lua-resty-mysql library? If yes, you should consult its documentation for details on the output results. Basically, it is documented in the read_query method's documentation:

https://github.com/agentzh/lua-resty-mysql#read_result

That is, by default, you should access a single field in the form res[row_num][column_name], for instance,

res[1]["id"]

accesses the "id" field in the 1st row of the resultset.

But also be aware of the "compact_arrays" option in the "connect" method:

https://github.com/agentzh/lua-resty-mysql#connect

Regards,
-agentzh

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[agentzh]

If I were you, I would just use libraries like lua-cjson to dump the data structures ;)

[StemonZhang]

Yeah, it's a good idea.
But I just want to get a single data from the DB, so if get the data structure, maybe the cost is a little big.

ÔÚ 2013-09-02 06:25:57£¬"Yichun Zhang" [email protected] дµÀ£º

If I were you, I would just use libraries like lua-cjson to dump the data structures ;)

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[agentzh]

@StemonZhang I'm suggesting using lua-cjson temporarily for your local debugging purposes, not for the formal output in the final product.

Anyway, I'm closing this.