SQL to/from JSON

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SQL to/from JSON

DuckDB provides functions to serialize and deserialize SELECT statements between SQL and JSON, as well as executing JSON serialized statements.

Function	Type	Description
`json_deserialize_sql(json)`	Scalar	Deserialize one or many `json` serialized statements back to an equivalent SQL string.
`json_execute_serialized_sql(varchar)`	Table	Execute `json` serialized statements and return the resulting rows. Only one statement at a time is supported for now.
`json_serialize_sql(varchar, skip_empty := boolean, skip_null := boolean, format := boolean)`	Scalar	Serialize a set of semicolon-separated (`;`) select statements to an equivalent list of `json` serialized statements.
`PRAGMA json_execute_serialized_sql(varchar)`	Pragma	Pragma version of the `json_execute_serialized_sql` function.

The json_serialize_sql(varchar) function takes three optional parameters, skip_empty, skip_null, and format that can be used to control the output of the serialized statements.

If you run the json_execute_serialize_sql(varchar) table function inside of a transaction the serialized statements will not be able to see any transaction local changes. This is because the statements are executed in a separate query context. You can use the PRAGMA json_execute_serialize_sql(varchar) pragma version to execute the statements in the same query context as the pragma, although with the limitation that the serialized JSON must be provided as a constant string, i.e., you cannot do PRAGMA json_execute_serialize_sql(json_serialize_sql(...)).

Note that these functions do not preserve syntactic sugar such as FROM * SELECT ..., so a statement round-tripped through json_deserialize_sql(json_serialize_sql(...)) may not be identical to the original statement, but should always be semantically equivalent and produce the same output.

Examples

Simple example:

SELECT json_serialize_sql('SELECT 2');

{"error":false,"statements":[{"node":{"type":"SELECT_NODE","modifiers":[],"cte_map":{"map":[]},"select_list":[{"class":"CONSTANT","type":"VALUE_CONSTANT","alias":"","value":{"type":{"id":"INTEGER","type_info":null},"is_null":false,"value":2}}],"from_table":{"type":"EMPTY","alias":"","sample":null},"where_clause":null,"group_expressions":[],"group_sets":[],"aggregate_handling":"STANDARD_HANDLING","having":null,"sample":null,"qualify":null}}]}

Example with multiple statements and skip options:

SELECT json_serialize_sql('SELECT 1 + 2; SELECT a + b FROM tbl1', skip_empty := true, skip_null := true);

{"error":false,"statements":[{"node":{"type":"SELECT_NODE","select_list":[{"class":"FUNCTION","type":"FUNCTION","function_name":"+","children":[{"class":"CONSTANT","type":"VALUE_CONSTANT","value":{"type":{"id":"INTEGER"},"is_null":false,"value":1}},{"class":"CONSTANT","type":"VALUE_CONSTANT","value":{"type":{"id":"INTEGER"},"is_null":false,"value":2}}],"order_bys":{"type":"ORDER_MODIFIER"},"distinct":false,"is_operator":true,"export_state":false}],"from_table":{"type":"EMPTY"},"aggregate_handling":"STANDARD_HANDLING"}},{"node":{"type":"SELECT_NODE","select_list":[{"class":"FUNCTION","type":"FUNCTION","function_name":"+","children":[{"class":"COLUMN_REF","type":"COLUMN_REF","column_names":["a"]},{"class":"COLUMN_REF","type":"COLUMN_REF","column_names":["b"]}],"order_bys":{"type":"ORDER_MODIFIER"},"distinct":false,"is_operator":true,"export_state":false}],"from_table":{"type":"BASE_TABLE","table_name":"tbl1"},"aggregate_handling":"STANDARD_HANDLING"}}]}

Example with a syntax error:

SELECT json_serialize_sql('TOTALLY NOT VALID SQL');

{"error":true,"error_type":"parser","error_message":"syntax error at or near \"TOTALLY\"","position":"0","error_subtype":"SYNTAX_ERROR"}

Example with deserialize:

SELECT json_deserialize_sql(json_serialize_sql('SELECT 1 + 2'));

SELECT (1 + 2)

Example with deserialize and syntax sugar, which is lost during the transformation:

SELECT json_deserialize_sql(json_serialize_sql('FROM x SELECT 1 + 2'));

SELECT (1 + 2) FROM x

Example with execute:

SELECT * FROM json_execute_serialized_sql(json_serialize_sql('SELECT 1 + 2'));

Example with error:

SELECT * FROM json_execute_serialized_sql(json_serialize_sql('TOTALLY NOT VALID SQL'));

Parser Error: Error parsing json: parser: syntax error at or near "TOTALLY"

Examples

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