mariadb 10.0.22 problem about crystal-mysql HOT 4 CLOSED

Hi @tophe . I added quoting-code to your comment to facilitate reading it.

When you use Database#query

db.query sql do |rs|
  # rs is a ResultSet, not a row.

  # you can ask column information, yes
  puts rs.column_name(0)

  # but you need to call ResultSet#each to iterate over the rows 
  rs.each do
    puts rs.read(Int32)
  end
end

Alternative you can use Database#query_one instead of Database#query that will return you a ResultSet alread positioned in the first row (it will also fail if more than 1 row is returned)

db.query_one sql do |rs|
  puts rs.column_name(0)
  puts rs.read(Int32)
end

Or if you just want the id Database#scalar will do it.

puts db.scalar sql

Your issue was calling ResultSet#read without calling first ResultSet#move_next.

from crystal-mysql.

Oh, thank you for that clean explanation !
I have reread the readme.md, and every thing was already there !
I close the issue .

from crystal-mysql.

just to be sure, right now we can read String with are nullable on mysql.
because if I write
lastname = rs.read(String)
and lastname is null on mysql I got:

Nil assertion failed (Exception)
[4950583] *CallStack::unwind:Array(Pointer(Void)) +87
[4950474] *CallStack#initialize:Array(Pointer(Void)) +10
[4950426] *CallStack::new:CallStack +42
[4841448] *raise:NoReturn +24
[4841422] ???
[5123328] *Nil#not_nil!:NoReturn +16
[5662846] *MySql::ResultSet +46
[5700726] *Finder::Store#store_build_mysql:DB::Database +550
[5699697] *Finder::Store#initialize<Finder::RMode, Logger::Severity, Int32>:(HTTP::Server::Response::Output | IO::FileDescriptor+ | Int32 | Nil) +1761
[5697905] *Finder::Store#initialize:mode:log_level<Finder::RMode, Logger::Severity>:(HTTP::Server::Response::Output | IO::FileDescriptor+ | Int32 | Nil) +49
[5697823] *Finder::Store::new:mode:log_level<Finder::RMode, Logger::Severity>:Finder::Store +127
[4798603] ???
[4859817] main +41
[139983727992517] __libc_start_main +245
[4791833] ???
[0] ???

from crystal-mysql.

@tophe use rs.read(String?) and generally T? for things that can be NULL in SQL (so nil in Crystal)

from crystal-mysql.