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Support "SELECT TOP n [PERCENT]... " queries.

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Updated the SQL parser to support "SELECT TOP n [PERCENT]... " queries,
matching the Mocrosoft Access SQL language.

Export these queries from databases with mdb-queries.
This commit is contained in:
James Woodcock
2020-09-26 11:28:34 +01:00
parent 8219e4ef7a
commit eb5dd4d0b7
5 changed files with 64 additions and 7 deletions
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2
src/sql/lexer.l
View File

@@ -72,6 +72,8 @@ null { return NUL; }
">" { return GT; }
like { return LIKE; }
limit { return LIMIT; }
top { return TOP; }
percent { return PERCENT; }
count { return COUNT; }
strptime { return STRPTIME; }
[ \t\r] ;

21
src/sql/mdbsql.c
View File

@@ -72,6 +72,7 @@ MdbSQL *sql;
sql->sarg_stack = NULL;
sql->max_rows = -1;
sql->limit = -1;
sql->limit_percent = 0;
return sql;
}
@@ -473,12 +474,23 @@ int mdb_sql_add_column(MdbSQL *sql, char *column_name)
sql->num_columns++;
return 0;
}
int mdb_sql_add_limit(MdbSQL *sql, char *limit)
int mdb_sql_add_limit(MdbSQL *sql, char *limit, int percent)
{
sql->limit = atoi(limit);
sql->limit_percent = percent;
if (sql->limit_percent && (sql->limit < 0 || sql->limit > 100)) {
return 1;
}
return 0;
}
int mdb_sql_get_limit(MdbSQL *sql)
{
return sql->limit;
}
int mdb_sql_add_function1(MdbSQL *sql, char *func_name, char *arg1)
{
fprintf(stderr, "calling function %s with %s", func_name, arg1);
@@ -833,6 +845,13 @@ int found = 0;
sql->cur_table = table;
mdb_index_scan_init(mdb, table);
/* We know how many rows there are, so convert limit percentage
* to an row count */
if (sql->limit != -1 && sql->limit_percent) {
sql->limit = (int)((double)table->num_rows / 100 * sql->limit);
sql->limit_percent = 0;
}
}
void

24
src/sql/parser.y
View File

@@ -62,7 +62,7 @@ typedef struct sql_context
%token <name> IDENT NAME PATH STRING NUMBER
%token SELECT FROM WHERE CONNECT DISCONNECT TO LIST TABLES AND OR NOT LIMIT COUNT STRPTIME
%token DESCRIBE TABLE
%token DESCRIBE TABLE TOP PERCENT
%token LTEQ GTEQ LIKE IS NUL
%type <name> database
@@ -91,7 +91,7 @@ stmt:
;
query:
SELECT column_list FROM table where_clause limit_clause {
SELECT top_clause column_list FROM table where_clause limit_clause {
mdb_sql_select(parser_ctx->mdb);
}
| CONNECT TO database {
@@ -108,6 +108,17 @@ query:
}
;
top_clause:
/* empty */
| TOP NUMBER { mdb_sql_add_limit(parser_ctx->mdb, $2, 0); free($2); }
| TOP NUMBER PERCENT {
if (mdb_sql_add_limit(parser_ctx->mdb, $2, 1)) {
yyerror(NULL, parser_ctx, "Percent values must be between 0 and 100");
}
free($2);
}
;
where_clause:
/* empty */
| WHERE sarg_list
@@ -115,7 +126,14 @@ where_clause:
limit_clause:
/* empty */
| LIMIT NUMBER { mdb_sql_add_limit(parser_ctx->mdb, $2); free($2); }
| LIMIT NUMBER {
if (mdb_sql_get_limit(parser_ctx->mdb) != -1) {
yyerror(NULL, parser_ctx, "Can not have TOP and LIMIT clauses");
} else {
mdb_sql_add_limit(parser_ctx->mdb, $2, 0);
}
free($2);
}
;
sarg_list: