Example script with creating 'exhcange_rates' table

Change-Id: Ia5142569961081dd86a6a257b390d1c4249004e1

samples/bq-queries/exchange_rates.sql

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+-- Copyright 2024 Google LLC
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--     https://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+/**
+  A script that you can use to get currency exchange rates in your
+  BigQuery scripts to join with.
+  It creates a table 'currency_rates' with columns:
+    currency_from and currency_to containing currency code pairs (e.g. USD, AED, ILS)
+    rate with conversion rate of 'currency_from' to 'currency_to'.
+
+  The table is built on a public Google Spreadsheet with actual data.
+  In that Spreadsheet conversion rates are fetched with GOOGLEFINANCE function regualrly.
+
+  Feel free to place the table where it works for you.
+  For instance, instead of using `gaarf.currency_rates` you can incorporate using
+  a macro for the target dataset to place the table together with other tables:
+  `{dst_dataset}.currency_rates_external`
+ */
+CREATE OR REPLACE EXTERNAL TABLE gaarf.currency_rates_external (
+  currency_from STRING,
+  currency_to STRING,
+  rate STRING
+)
+OPTIONS (
+  format = 'GOOGLE_SHEETS',
+  skip_leading_rows = 1,
+  sheet_range = "TABLE",
+  uris = ["https://docs.google.com/spreadsheets/d/1Up8zK3JhoE2zI1n0koi-LQcm6J7-o_slBht3SgVkJYA/edit?usp=sharing"],
+  description = "External table for current currency exchange rates generated by Google Finance."
+);
+
+-- Create a view that casts the rate to NUMERIC
+CREATE OR REPLACE VIEW gaarf.currency_rates AS
+SELECT
+  currency_from,
+  currency_to,
+  IFNULL(CAST(rate AS NUMERIC), 1) AS rate
+FROM gaarf.currency_rates_external;