SAPHANA学习（11）：SQL Function(J)

80.JSON_QUERY

JSON_QUERY(

  <JSON_API_common_syntax>

  [ <JSON_output_clause> ]

  [ <JSON_query_wrapper_behavior> ]

  [ <JSON_query_empty_behavior> ON EMPTY ]

  [ <JSON_query_error_behavior> ON ERROR ]

 )

<JSON_API_common_syntax> ::= <JSON_context_item>, <JSON_path_specification>

JSON_context_item

Specifies the JSON document to operate on, such as a table column, string, or collection.

JSON_path_specification

<JSON_path_specification> ::= <JSON_path_mode> <JSON_path_wff>

<JSON_path_mode> ::= STRICT | LAX

<JSON_path_wff> indicates an actual JSON path (for example, '$.item1').

<JSON_path_specification> does not use double quotes.

<JSON_output_clause> ::= RETURNING <data_type>

返回类型：

Supported data types: NVARCHAR(<length>), VARCHAR(<length>).

<JSON_query_wrapper_behavior> WRAPPER

<JSON_query_wrapper_behavior> ::=

  WITHOUT [ ARRAY ]

  | WITH [ CONDITIONAL | UNCONDITIONAL ] [ ARRAY ]

默认WITHOUT ARRAY WRAPPER，如果是WITH,默认WITH UNCONDITIONAL ARRAY WRAPPER

<JSON_query_empty_behavior> ON EMPTY

<JSON_query_empty_behavior> ::=

 ERROR | NULL | EMPTY ARRAY

  | EMPTY OBJECT

默认NULL ON EMPTY

ERROR ON EMPTY:返回错误，如果没有指定值；

NULL ON EMPTY：返回空；

EMPTY ARRAY ON EMPTY:返回empty array;

EMPTY OBJECT ON EMPTY:返回empty object;

<JSON_query_error_behavior> ON ERROR

<JSON_query_error_behavior> ::=

 ERROR | NULL | EMPTY ARRAY

  | EMPTY OBJECT

默认NULL ON ERROR,

当query出现error时，返回动作；

ERROR ON ERROR:返回error,当返回值报错

NULL ON ERROR:返回null;

EMPTY ARRAY ON ERROR:返回empty array;

EMPTY OBJECT ON ERROR:返回empty object;

JSON符号：

$：第一个字符；

.:成员运算符，访问成员；

[]:

to:array,示例：$.item[1 to 3];

*:所有成员，示例：$.*.item[*];

JSON_TABLE(

  <JSON_API_common_syntax>

  <JSON_table_columns_clause>

  [ <JSON_table_error_behavior> ON ERROR ]

  )

<JSON_table_columns_clause> ::=

  COLUMNS ( <JSON_table_column_definition> [,... ] )

<JSON_table_column_definition> ::=

 <JSON_table_ordinality_column_definition>

  | <JSON_table_regular_column_definition>

  | <JSON_table_formatted_column_definition>

  | <JSON_table_nested_columns>

<JSON_table_ordinality_column_definition> ::= <column_name> FOR ORDINALITY

生成序号列

<JSON_table_regular_column_definition> ::= <column_name> <data_type>

  PATH <JSON_table_column_path_specification>

  [ JSON <table_column_empty_behavior> ON EMPTY ]

  [ JSON_table_column_error_behavior> ON ERROR ]

生成普通列

<JSON_table_column_path_specification> ::= <JSON_path_specification>

获取json值的路径

<JSON_table_column_empty_behavior> ::= ERROR | NULL | DEFAULT <value_expression>

当创建列为空时，执行操作，ERROR：返回error;NULL：返回null;DEFAULT:返回默认值

<JSON_table_column_error_behavior> ::= ERROR | NULL | DEFAULT <value_expression>

当创建列出错时，执行操作；

<JSON_table_formatted_column_definition> ::=

  <column_name> <data_type>

  FORMAT <JSON_representation>

  PATH <JSON_table_column_path_specification>

  [ <JSON_table_formatted_column_wrapper_behavior> WRAPPER ]

  [ <JSON_table_formatted_column_empty_behavior> ON EMPTY ]

  [ <JSON_table_formatted_column_error_behavior> ON ERROR ]

<data_type>只支持VARCHAR(<n>),NVARCHAR(<n>)

<JSON_representation> ::= JSON | JSON ENCODING { UTF8 } | JSON ENCODING { UTF16 } | JSON ENCODING { UTF32 }

设置格式

<JSON_table_nested_columns> ::= NESTED [ PATH ]

 <JSON_table_nested_path_specification>

 <JSON_table_columns_clause>

 <JSON_table_nested_path_specification> ::= <JSON_path_specification>

JSON_VALUE(

  <JSON_API_common_syntax>

  [ <JSON_returning_clause> ]

  [ <JSON_value_empty_behavior> ON EMPTY ]

  [ <JSON_value_error_behavior> ON ERROR ]

  )

<JSON_returning_clause> ::= RETURNING <data_type>

 <data_type> ::=

 INTEGER  | BIGINT  | DECIMAL

  | VARCHAR(<integer>)

  | NVARCHAR(<integer>)

*/

--返回 {"item1":1,"item2":2,"item3":3}
--SELECT JSON_QUERY('{"item1":1, "item2":2, "item3":3}', '$') FROM DUMMY;
--返回[1]
--SELECT JSON_QUERY('{"item1":1, "item2":2, "item3":3}', '$.item1' WITH WRAPPER)  FROM DUMMY;
CREATE ROW TABLE TEST_JSON (A INT, B NVARCHAR(5000));
INSERT INTO TEST_JSON VALUES (1,
       '{
       "PONumber": 1,
       "Reference": "BSMITH-74635645",
       "Requestor": "Barb Smith",
       "User": "BSMITH",       
       "CostCenter": "A50",       
       "ShippingInstructions":{
              "name": "Barb Smith", 
              "Address":{
                     "street": "100 Fairchild Ave",
                     "city": "San Diego",
                     "state": "CA","zipCode": 23345,
                     "country": "USA"
              },                      
              "Phone": [{"type": "Office", "number": "519-555-6310"}]
       },      
       "SpecialInstructions": "Surface Mail",      
       "LineItems": [
              {
              "ItemNumber": 1,
              "Part": {"Description": "Basic Kit", "UnitPrice": 19.95, "UPCCode": 73649587162},
              "Quantity": 7
              },              
              {
              "ItemNumber": 2,
              "Part": {"Description": "Base Kit 2", "UnitPrice": 29.95, "UPCCode": 83600229374},
              "Quantity": 1
              },              
              {
              "ItemNumber": 3,
              "Part": {"Description": "Professional", "UnitPrice": 39.95, "UPCCode": 33298003521},
              "Quantity": 8
              },             
              {
              "ItemNumber": 4,
              "Part": {"Description": "Enterprise", "UnitPrice": 49.95, "UPCCode": 91827739856},
              "Quantity": 8
              },              
              {"ItemNumber": 5,
              "Part": {"Description": "Unlimited", "UnitPrice": 59.95, "UPCCode": 22983303876},
              "Quantity": 8
              }
              ]
       } '
);
/*
SELECT JT.* FROM JSON_TABLE(TEST_JSON.B, '$.LineItems[*]'
       COLUMNS (       
              RN FOR ORDINALITY,       
              ITEM_NUMBER INT PATH '$.ItemNumber',       
              UPC_CODE BIGINT PATH '$.Part.UPCCode'   
              )
 ) AS JT;

SELECT * FROM JSON_TABLE(TEST_JSON.B, '$.ShippingInstructions'
      COLUMNS ( PHONE VARCHAR(50) FORMAT JSON PATH '$.Phone' )
 ) AS JT;
 */
--不存在？
--SELECT JSON_VALUE('{"item1":10}', '$.item1') AS "value" FROM DUMMY;
--SELECT JSON_VALUE('[0, 1, 2, 3]', '$[0]') AS "value"  FROM DUMMY;
--SELECT JSON_VALUE('{"item":"string"}', '$.item' RETURNING DECIMAL ERROR ON ERROR) AS "Item" FROM DUMMY;
--SELECT JSON_VALUE('{"firstname":"John"}', '$.lastname' DEFAULT 'No last name found' ON EMPTY) AS "Last Name" FROM DUMMY;
--SELECT JSON_VALUE('{"firstname":"John"}', 'strict $.lastname' ERROR ON ERROR) AS "Last Name" FROM DUMMY;