# Modes Here are the various loading modes available. All modes load into a new temporary table prior to final load.

Mode	Description
`full-refresh`	This is the default mode. The target table will be dropped and recreated with the source data.
`incremental`	The source data will be merged or appended into the target table. If the table does not exist, it will be created. See below for more details.
`truncate`	Similar to `full-refresh`, except that the target table is truncated instead of dropped. This keeps any special DDL / GRANT applied.
`snapshot`	Appends the full dataset with an added timestamp column. If the target table exists, Sling will insert into / append data with a `_sling_loaded_at` column. If it does not, the table will be created.
`backfill`	Similar to `incremental`, but takes a `range` input to backfill a specific `update_key` range, such as dates or numbers.
`definition-only`	Creates the target table or file structure without transferring any data. For database targets, the table is created with the inferred schema but 0 rows. For file targets, only Parquet and Arrow formats are supported, creating a file with proper column types but no data rows.
`change-capture`	Captures row-level changes (inserts, updates, deletes) from the source database's transaction log. Performs an automatic initial snapshot on the first run, then reads incremental changes on subsequent runs. Requires a `primary_key`. See Change Capture (CDC) for details.

### Incremental Mode Strategies

Load Strategy	Primary Key	Update Key	Stream Strategy
New Data Upsert (update/insert)	`yes`	`yes`	Only new records after `max(update_key)`
Full Data Upsert (update/insert)	`yes`	no	Full data
Append Only (insert, no update)	no	`yes`	Only new records after `max(update_key)`

### Incremental or Backfill Mode With Custom SQL When using `incremental` or `backfill` mode with a custom SQL stream, Sling provides two placeholder options to handle incremental loading: * `{incremental_where_cond}`: Injects a complete WHERE condition * `{incremental_value}`: Injects only the value, allowing for custom condition logic #### Using {incremental\_where\_cond} This placeholder injects a complete WHERE condition based on the `update_key`: ```sql SELECT * FROM my_schema.my_table WHERE {incremental_where_cond} ``` Sling will replace the placeholder as follows: * First run (table doesn't exist): `WHERE 1=1` * Subsequent runs: `WHERE my_update_key > '[incremental_value]'` For example, if the last maximum value was '2001-01-01 01:01:01', the query becomes: ```sql SELECT * FROM my_schema.my_table WHERE my_update_key > '2001-01-01 01:01:01' ``` #### Using {incremental\_value} This placeholder gives you more control over the WHERE condition by injecting only the value: ```sql SELECT * FROM my_schema.my_table WHERE my_int_key > coalesce({incremental_value}, 0) -- For numeric columns -- or WHERE my_timestamp > coalesce({incremental_value}, '2001-01-01') -- For timestamp columns ``` Sling will replace the placeholder as follows: * First run (table doesn't exist): `{incremental_value}` becomes `null` * Subsequent runs: `{incremental_value}` becomes the last maximum value For example, if the last maximum value was 99, the query becomes: ```sql SELECT * FROM my_schema.my_table WHERE my_int_key > coalesce(99, 0) ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.slingdata.io/concepts/replication/modes.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.