使用ANTLR4解析T-SQL查询

Question

我目前正在为我的学校项目开发一个T-SQL解析器，它将能够映射数据库中的查询。到目前为止，我已经设法解析大部分，但我有一个问题，我似乎无法解决…我正在使用c#和tsql。g4语法和ANTLR4.

如何访问表达式?我想知道我在select中并且我有某种表达式，但是表达式是什么类型的呢?是否可以从select_statement中仅提取列名、模式(如果有)和数据库(如果有)?

当我试图从c#代码中访问表达式时:

环境:GrammarSQLParser.Dml_clauseContext context.select_list .query_specification .query_expression context.select_statement () () () () .select_list_elem () .expression ()

我只得到CopyFrom()方法，我没有任何full_column_name()方法来访问进一步的table_name()等.

edit1:仔细检查后，表达式是一个column_ref_expression，但我如何从表达式访问它?它们是不同的对象。

这是查询:

select p.BusinessEntityID,p.FirstName,p.LastName,adresstbl.* from person.Person as p 
join (select bea.BusinessEntityID, adr.AddressLine1, adr.AddressLine2, adr.City, adr.PostalCode from person.BusinessEntityAddress as bea 
join person.Address as adr
on bea.AddressID = adr.AddressID )
as adresstbl 
on not p.BusinessEntityID != adresstbl.BusinessEntityID order by p.BusinessEntityID

这是我的解析树:

Lisp解析树:(tsql_file (batch (sql_clauses (sql_clause .)(dml_clause (select_statement (query_expression)select (select_list (select_list_elem (expression(table_name (id (simple_id p)))。(id (simple_id BusinessEntityID))))) .， (select_list_elem (expression) (full_column_name (table_name (id . s)(simple_id p))。(id (simple_id FirstName)))))， (select_list_elem .)(expression (full_column_name (table_name (id (simple_id p)))) .)(id(simple_id LastName)))))， ) (select_list_elem (table_name (id . m)(simple_id addresstbl)))。*)) from (table_sources (table_source . stable_source_item_joined (table_source_item(table_name (id (simple_id person))。(id (simple_id Person))))(as_table_alias as (table_alias) id (simple_id p))))) (join_part join .)(table_source_item_joined (table_source_item . joinselect (select) _statement (query_expression)(query_expression (query_specification)(select_list_elem (expression) (full_column_name (table_name)(simple_id bea)))。(id (simple_id BusinessEntityID)))))，(select_list_elem (expression) (full_column_name (table_name)(simple_id adr)))。(id (simple_id AddressLine1)))))，(select_list_elem (expression) (full_column_name (table_name)(simple_id adr)))。(id (simple_id AddressLine2)))))，(select_list_elem (expression) (full_column_name (table_name)(simple_id adr)))。(id (simple_id城市)))))，(select_list_elem . 0)(expression (full_column_name (table_name (id (simple_id adr)))) .)(id(simple_id PostalCode)))))) from (table_sourcestable_source_item_joined (table_source_item(table_name (id (simple_id person))。(id (simple_idBusinessEntityAddress)))) (as_table_alias as (table_alias)(simple_id bea)))))) (join_part join (table_source . nettable_source_item_joined (table_source_item(table_name (id (simple_id person))。(id (simple_id地址))))(as_table_alias as (table_alias) (id (simple_id adr))))))))搜索条件(search_condition_and search_condition_not(predicate (expression) full_column_name (table_name (id (simple_id . id)bea)))。(id (simple_id AddressID)))) (comparison_operator =))(expression (full_column_name (table_name (id (simple_id adr)))) .)(id(simple_id AddressID )))))))))))))) ))))) ( as_table_alias作为(table_alias (id (simple_id addresstbl)))))))) on (search_condition . net)(search_condition_and (search_condition_not not)(full_column_name (table_name (id (simple_id p))))。(id (simple_idBusinessEntityID)))) (comparison_operator !)=)(表达式(full_column_name (table_name (id (simple_id addresstbl))) .)(id(simple_id BusinessEntityID)))))))))))))) (order_by_clause order by .(order_by_expression (expression) full_column_name (table_name (id .)(simple_id p))。(id (simple_id BusinessEntityID))))))))))))

)

Answer 1

expression可能是许多事情之一。如果你看一下语法，你会看到

expression
    : DEFAULT                                                  #primitive_expression
    | NULL                                                     #primitive_expression
    | LOCAL_ID                                                 #primitive_expression
    | constant                                                 #primitive_expression
    | function_call                                            #function_call_expression
    | expression COLLATE id                                    #function_call_expression
    | case_expr                                                #case_expression
    | full_column_name                                         #column_ref_expression
    | '(' expression ')'                                       #bracket_expression
    | '(' subquery ')'                                         #subquery_expression
    | '~' expression                                           #unary_operator_expression
    | expression op=('*' | '/' | '%') expression               #binary_operator_expression
    | op=('+' | '-') expression                                #unary_operator_expression
    | expression op=('+' | '-' | '&' | '^' | '|') expression   #binary_operator_expression
    | expression comparison_operator expression                #binary_operator_expression
    ;

你需要弄清楚这是哪件事。在您的情况下，它是一个column_ref_expression，在这种情况下，您需要将其转换为Column_ref_expressionContext，然后您将能够访问full_column_name。

有多种方法可以确定它是哪个，或者如果您只想支持语法的有限子集，则可以假设。