Merge pull request #1718 from ilianiliev-redis/RDSC-3630-using-sql-case

RDSC-3630 Adding SQL Case examples

Author: andy-stark-redis

content/integrate/redis-data-integration/data-pipelines/transform-examples/redis-sql-case-example.md

@@ -0,0 +1,63 @@
+---
+Title: Using SQL CASE
+aliases: /integrate/redis-data-integration/ingest/data-pipelines/transform-examples/redis-sql-case-example/
+alwaysopen: false
+categories:
+- docs
+- integrate
+- rs
+- rdi
+description: null
+group: di
+linkTitle: Using SQL CASE
+summary: Redis Data Integration keeps Redis in sync with the primary database in near
+  real time.
+type: integration
+weight: 30
+---
+
+The [`CASE`](https://www.w3schools.com/sql/sql_case.asp) statement allows you to specify conditions and return different values based on those conditions. You can use it both to create new fields or filter existing data.
+
+## Using SQL CASE to create a new field
+The example below demonstrates how to use the `CASE` statement to create a new field called `Market` based on the value of the `BillingCountry` field in the `Invoice` table. The new field categorizes countries into regions such as "North America" and "Europe".
+
+```yaml
+source:
+  table: Invoice
+
+transform:
+  - uses: add_field
+    with:
+      field: "Market"
+      language: sql
+      expression: |
+        CASE
+          WHEN BillingCountry = 'USA' THEN 'North America'
+          WHEN BillingCountry = 'Canada' THEN 'North America'
+          WHEN BillingCountry = 'UK' THEN 'Europe'
+          WHEN BillingCountry = 'France' THEN 'Europe'
+          ELSE 'Other'
+        END
+```
+
+## Using SQL CASE to filter data
+
+You can also use the `CASE` statement to filter data based on specific conditions. The example below demonstrates how to filter the `Invoice` table to include only invoices from the USA and Canada that have a `Total` value above their country-specific threshold.
+
+Because the `Total` field is a Decimal in the source table, it is represented as a string in Debezium and so you must cast it to `REAL` to compare it numerically in the `CASE` statement. Without this cast, it will be compared as a string value, which will give the wrong result.
+
+```yaml
+source:
+  table: Invoice
+
+transform:
+  - uses: filter
+    with:
+      language: sql
+      expression: |
+        CASE
+          WHEN BillingCountry = 'USA' AND CAST(Total AS REAL) > 11.99 THEN True
+          WHEN BillingCountry = 'Canada' AND CAST(Total AS REAL) > 9.99 THEN True
+          ELSE False
+        END
+```