Create 19_show_create_table.md

19_show_create_table.md

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+# Advent of Flink - Day 19 `SHOW CREATE TABLE`
+
+A quick one about another default debugging toool: `SHOW CREATE TABLE`. `SHOW CREATE TABLE` is an extremely important command for debugging and support. 
+`SHOW CREATE TABLE <table>` shows  the `CREATE TABLE` statement that creates the named table. For example, if we create a table like this. 
+```sql
+CREATE TABLE products AS SELECT * FROM `examples`.`marketplace.`.`products`;
+````
+And then run
+```sql
+SHOW CREATE TABLE products;
+```
+it will return
+```sql
+CREATE TABLE `<catalog>`.`<database>`.`products` (
+  `product_id` VARCHAR(2147483647) NOT NULL,
+  `name` VARCHAR(2147483647),
+  `brand` VARCHAR(2147483647),
+  `vendor` VARCHAR(2147483647),
+  `department` VARCHAR(2147483647),
+  CONSTRAINT `PRIMARY` PRIMARY KEY (`product_id`) NOT ENFORCED
+)
+DISTRIBUTED BY HASH(`product_id`) INTO 4 BUCKETS
+WITH (
+  'changelog.mode' = 'upsert',
+  'connector' = 'confluent',
+  'kafka.cleanup-policy' = 'delete',
+  'kafka.max-message-size' = '2097164 bytes',
+  'kafka.retention.size' = '0 bytes',
+  'kafka.retention.time' = '7 d',
+  'key.format' = 'avro-registry',
+  'scan.bounded.mode' = 'unbounded',
+  'scan.startup.mode' = 'earliest-offset',
+  'value.format' = 'avro-registry'
+)
+```
+
+This is valuable in two ways. 
+
+1. It shows you and anyone your sharing this output with all the table options, constraints, distribution keys that were automatically derived when the table was created.
+   The most important ones being the primary keys and the changelog mode.
+3. You can share the `CREATE TABLE` statement with anyone who needs to reproduce an error that you are seeing. For example, if I was supporting a
+   customer and the customer experienced some parser or optimizer error when submitting a statement, I would first ask for the output of
+   `SHOW CREATE TABLE` for all involved tables, because that allows me to easily re-create the same tables that the customer is using and then run the
+   same query that the customer is having issues with. I don't have any data in input tables yet, but at least the query compiles for me, too, which
+   is often already enough but in anycase the first step.
+
+By the way, you can also use `SHOW CREATE TABLE` on the tables in the `examples` catalog, to see how this data is generated. 
+```sql
+CREATE TABLE `examples`.`marketplace`.`products` (
+  `product_id` VARCHAR(2147483647) NOT NULL,
+  `name` VARCHAR(2147483647) NOT NULL,
+  `brand` VARCHAR(2147483647) NOT NULL,
+  `vendor` VARCHAR(2147483647) NOT NULL,
+  `department` VARCHAR(2147483647) NOT NULL,
+  CONSTRAINT `PK_product_id` PRIMARY KEY (`product_id`) NOT ENFORCED
+)
+WITH (
+  'changelog.mode' = 'upsert',
+  'connector' = 'faker',
+  'fields.brand.expression' = '#{Commerce.brand}',
+  'fields.department.expression' = '#{Commerce.department}',
+  'fields.name.expression' = '#{Commerce.productName}',
+  'fields.product_id.expression' = '#{Number.numberBetween ''1000'',''1500''}',
+  'fields.vendor.expression' = '#{Commerce.vendor}',
+  'rows-per-second' = '50'
+)
+```
+
+That's already it for today. As always (so far), the examples in here are runnable out of the box on [Confluent Cloud](https://confluent.cloud).
+