给一个变量赋返回的唯一值

我正在学习LUA和SQL语句。我尝试了一下,可以显示SELECT或执行UPDATE、INSERT等操作,但我不知道如何将返回的唯一SELECT值赋给一个变量。

mysql = require "luasql.mysql"

env = mysql.mysql()
conn = env:connect('table','user','pass','server')
--print(env,conn)

cursor,errorString = conn:execute([[select id from agent where extension = '9072']])
--print(cursor,errorString)

row = cursor:fetch ({}, "a")

while row do
   print(string.format("%s", row.id))
   row = cursor:fetch (row, "a")
end

-- close everything
cursor:close()
conn:close()
env:close()

我希望得到类似这样的东西: value=33

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用户7552
用户7552

我会这样做

sql = "select id from agent where extension = '9072' limit 1"
cursor,errorString = conn:execute(sql)
value = nil
if cursor then
  row = cursor:fetch ({}, "a")    -- 我们将有0或1行
  if row then value = row.id end
end
2019-05-22 13:15:16