Add force_not_null and force_null options to the copy.md page

content/references/sqlreference/statements/copy.md

@@ -18,26 +18,48 @@ copy movies2 from 'movies_backup.csv';
 
 Copy supports a number of options controlling the format.
 
-* `Format`:  
+* `Format`:
   `csv`, `text`, `binary`. Only for copy to: `numpy`.
-* `Delimiter`:  
+* `Delimiter`:
   The record separator for `text` and `csv` formats.
   By default `\t`, and `,`.
-* `Header`:  
+* `Header`:
   If the `text` and `csv` has a header.
   By default `false`.
-* `Null`:  
+* `Null`:
   The string that represents a `null` value in `text` and `csv` formats.
   By default `\N`, and empty string.
-* `Quote`:  
+* `Quote`:
   The quoting character for the `csv` format. By default `"`.
   This can be used to insert values containing the delimiter.
-* `Escape`:  
+* `Escape`:
   The escape character for the `csv` format. By default `"`.
   This can be used to escape the quote character.
+* `Force Not Null`:
+  Do not match the specified columns' values against the null string. In the default case where the null string is empty, this means that empty values will be read as zero-length strings rather than nulls, even when they are not quoted. If `*` is specified, the option will be applied to all columns. This option is allowed only in `COPY FROM`, and only when using `csv` format.
+* `Force Null`:
+  Match the specified columns' values against the null string, even if it has been quoted, and if a match is found set the value to `NULL`. In the default case where the null string is empty, this converts a quoted empty string into NULL. If `*` is specified, the option will be applied to all columns. This option is allowed only in `COPY FROM`, and only when using `csv` format.
+  {{< callout type="info" >}}Note: `FORCE_NULL` and `FORCE_NOT_NULL` can be used simultaneously on the same column. This results in converting quoted null strings to null values and unquoted null strings to empty strings.{{< /callout >}}
 
 CedarDB also supports a best-effort import mode:
 
 * `(on_error ignore)`:
   By default, Copy aborts when encountering invalid rows.
   With this option, rows containing mismatching elements will be skipped on a best-effort basis.
+
+A query that uses all available copy options could look like this:
+```sql
+COPY target_table (column1, column2, column3)
+FROM '/absolute/path/to/your_file.csv'
+WITH (
+    FORMAT csv,
+    DELIMITER ',',
+    HEADER true,
+    NULL 'null',
+    QUOTE '"',
+    ESCAPE '\',
+    FORCE_NOT_NULL (column1, column2),
+    FORCE_NULL (column3),
+    ON_ERROR ignore
+);
+```