SQL::Translator, sqlt-diff confusion I have many schema I wish to compare,
SQL::Translator::Manual shows this example sqlt-diff foo-v1.sql=MySQL foo-v2.sql=Oracle > diff.sql.

How do I generate schemas required for foo-v1.sql and foo-v2.sql?

What do you mean ? schema are something you write (or someone gives you)

If you have an existing database and you can connect to it with sqlt as documented :)

the short docs

  DBI Parser Options:
  sqlt -f|--from|--parser MySQL
       -t|--to|--producer Oracle
       [options]
       file [file2 ...]

    --dsn              DSN for connecting to database
                       (see also --use-same-auth below)
    --db-user          Database user
    --db-password      Database password
[download]

Which you can use like

$ sqlt -f DBI-SQLite --db-user "" --db-password "" --dsn dbi:SQLite:te
+mp.sqlite -t SQLite
--
-- Created by SQL::Translator::Producer::SQLite
-- Created on Thu Oct  2 16:00:34 2014
--

BEGIN TRANSACTION;

--
-- Table: "trains"
--
CREATE TABLE "trains" (
  "A" text NOT NULL,
  "B" text NOT NULL,
  "C" real NOT NULL,
  "D" text NOT NULL,
  "E" text NOT NULL,
  "F" real NOT NULL,
  "G" real NOT NULL
);

COMMIT;


$ sqlt -f DBI-SQLite --db-user "" --db-password "" --dsn dbi:SQLite:db
+idbd.anydata.tsv.temp.sqlite -t Oracle
--
-- Created by SQL::Translator::Producer::Oracle
-- Created on Thu Oct  2 16:02:17 2014
--
--
-- Table: trains
--;

CREATE TABLE "trains" (
  "A" clob NOT NULL,
  "B" clob NOT NULL,
  "C" real NOT NULL,
  "D" clob NOT NULL,
  "E" clob NOT NULL,
  "F" real NOT NULL,
  "G" real NOT NULL
);

/
[download]

The long better docs https://metacpan.org/pod/distribution/SQL-Translator/lib/SQL/Translator/Manual.pod#EXTRACT-SQL-SCHEMAS-DIRECTLY-FROM-DATABASE

  $ sqlt -f DBI --dsn dbi:mysql:FOO --db-user guest \
    --db-password p4ssw0rd -t PostgreSQL > foo
[download]

This usage is waaay easier :)

$ sqlt -f DBI --db-user "" --db-password "" --dsn dbi:SQLite:dbidbd.an
+ydata.tsv.temp.sqlite -t Oracle
--
-- Created by SQL::Translator::Producer::Oracle
-- Created on Thu Oct  2 16:07:59 2014
--
--
-- Table: trains
--;

CREATE TABLE "trains" (
  "A" clob NOT NULL,
  "B" clob NOT NULL,
  "C" real NOT NULL,
  "D" clob NOT NULL,
  "E" clob NOT NULL,
  "F" real NOT NULL,
  "G" real NOT NULL
);

/


$ sqlt -f DBI --db-user "" --db-password "" --dsn dbi:SQLite:dbidbd.an
+ydata.tsv.temp.sqlite -t Sybase
--
-- Created by SQL::Translator::Producer::Sybase
-- Created on Thu Oct  2 16:08:02 2014
--
--
-- Table: trains
--

CREATE TABLE trains (
  A varchar(255) NOT NULL,
  B varchar(255) NOT NULL,
  C double precision NOT NULL,
  D varchar(255) NOT NULL,
  E varchar(255) NOT NULL,
  F double precision NOT NULL,
  G double precision NOT NULL
);


$ sqlt -f DBI --db-user "" --db-password "" --dsn dbi:SQLite:dbidbd.an
+ydata.tsv.temp.sqlite -t MySQL
--
-- Created by SQL::Translator::Producer::MySQL
-- Created on Thu Oct  2 16:08:07 2014
--
SET foreign_key_checks=0;

--
-- Table: `trains`
--
CREATE TABLE `trains` (
  `A` text NOT NULL,
  `B` text NOT NULL,
  `C` double NOT NULL,
  `D` text NOT NULL,
  `E` text NOT NULL,
  `F` double NOT NULL,
  `G` double NOT NULL
);

SET foreign_key_checks=1;
[download]