Create openresty-odbc-connection.md

Connect-with-Exasol/openresty-odbc-connection.md

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+# OpenResty Exasol ODBC connection
+
+## Background
+
+Connecting to Exasol from OpenResty lets you build fast APIs or dynamic web endpoints directly inside Nginx using Lua.
+This enables you to query Exasol on the fly and return results to clients without an extra backend layer.
+
+## Steps
+
+Below are steps to connect to Exasol from Openresty.
+
+* Install openresty [Openresty Installation manual](https://openresty.org/en/linux-packages.html#ubuntu)
+* install Luarocks
+
+```shell
+wget https://github.com/luarocks/luarocks/archive/v3.0.0.tar.gz
+
+tar zxvf v3.0.0.tar.gz
+
+./configure --prefix=/usr/local/openresty/luajit/ --with-lua=/usr/local/openresty/luajit/ --lua-suffix=jit --with-lua-include=/usr/local/openresty/luajit/include/luajit-2.1
+
+sudo make build
+
+sudo make install
+```
+
+* install ODBC package in luarocks
+
+```shell
+luarocks install odbc
+```
+
+* install Exasol ODBC driver, create DSN for Exasol DB [ODBC Drivers for Linux/FreeBSD | Exasol Documentation](https://docs.exasol.com/db/latest/connect_exasol/drivers/odbc/odbc_linux.htm)
+
+* Execute connection test scripts
+
+ odbctest.sh
+
+```shell
+# set -x
+# ORHOME is the path to the OpenResty install
+export ORHOME="/usr/local/openresty"
+export ODBCINI="${ORHOME}/odbc/.odbc.ini"
+export LD_LIBRARY_PATH="${ORHOME}/luajit/lib"
+export PATH="$PATH:${ORHOME}/bin/"
+resty odbctest.lua $1
+echo "Retun code from resty $?"
+```
+
+ odbctest.lua
+
+```lua
+local odbc = require("odbc")
+local call = [[select * from sys.exa_all_tables]]
+print("Using dsn " .. arg[1])
+local DSN = arg[1]
+   print("About to connect")
+local cnn,err = odbc.connect(DSN)
+if cnn == nil then
+   print("Failed to connect" .. err.message)
+else
+   print("Connected")
+end
+local stmt,err = cnn:statement()
+if stmt == nil then
+   print("Failed to prepare Statement" ..err.message)
+else
+   print("Prepared statement" )
+end
+local ret,err = stmt:execute(call)
+if ret == nil then
+   print("Failed to execute statement" .. err.message)
+else
+   print("Executed satement")
+end
+local cols = ret:colnames()
+if string.upper(cols[1]) == [[ERR]] then
+   -- There has been some sort of error
+   print("Some sort of error was raised " .. ret:fetch())
+end
+```
+
+## Additional References
+
+* [Openresty Installation manual](https://openresty.org/en/linux-packages.html#ubuntu)
+* [ODBC Drivers for Linux/FreeBSD | Exasol Documentation](https://docs.exasol.com/db/latest/connect_exasol/drivers/odbc/odbc_linux.htm)
+
+*We appreciate your input! Share your knowledge by contributing to the Knowledge Base directly in [GitHub](https://github.com/exasol/public-knowledgebase).*