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In addition to executing SQL statements directly, Iguana offers another method for writing to databases using a Database Schema File (*.vdb), db.tables{} and the conn:merge{} function.

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Info
`conn:merge{}` does not support spaces in column names. If your database schema contains spaces in column names, you’ll need to modify the column names to remove or replace spaces before using `conn:merge{}` or see https://help.interfaceware.com/v6/customize-custom_merge-lua-for-table-and-field-names-with-spaces.

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title	Error Handling Merges

The merge process all happens within a single database transaction. If it fails, the transaction is rolled back and nothing is altered in the database. This behavior can be optionally turned off if you pass in transaction=false as an argument.

Just like with conn:execute{}, you can use pcall() to catch and gracefully handle any errors that arise from conn:merge{} operations:

Code Block

language	lua

function doMerge(conn, T) 
  local R = conn:merge{data=T, live=true}
end 

function main()
  -- create empty table
  local T = db.tables{vdb='report.vdb, name ='Patients'} 
  
  -- map vdb table values
  T.Patients[1].FirstName = 'John' 
  T.Patients[1].LastName = 'Doe' 
  T.Patients[1].ID = 1
  
  -- call merge function and handle response
  local Success, R = pcall(doMerge, conn, T) 
  if not Success then 
    iguana.log('Error during merge: ', R.message) 
  end
end

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