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C Client Library
- Query execution functions
- size_t PQescapeString (char *to, const char *from, size_t length)
- Escape an untrusted string
- PGresult *PQexec(PGconn *conn, const char *query)
- query is query text
- Returns result handle
- ExecStatusType PQresultStatus(const PGresult *res)
- Check status of a result handle
- PGRES_EMPTY_QUERY, PGRES_COMMAND_OK, PGRES_TUPLES_OK, PGRES_COPY_OUT, PGRES_COPY_IN, PGRES_BAD_RESPONSE, PGRES_NONFATAL_ERROR, PGRES_FATAL_ERROR
- int PQntuples(const PGresult *res) - number of tuples in result
- int PQnfields(const PGresult *res) - number of fields in result
- char* PQgetvalue(const PGresult *res,int tup_num,int field_num) - get a field
- char *PQresultErrorMessage(const PGresult *res) - return most recent error string
- void PQclear(PQresult *res) - free underlying memory consumed by result set
01 #include "libpq-fe.h"
02 #include <string.h>
03
04 int main(void)
05 {
06 PGconn *conn;
07 PGresult *res;
08 int i,j;
09 conn = PQconnectdb("user=postgres dbname=a");
10 if(PQstatus(conn) == CONNECTION_BAD) {
11 fprintf(stderr,"Connection failed: %s\n",PQerrorMessage(conn));
12 exit(1);
13 }
14
15 res = PQexec(conn,"SELECT id,firstname,lastname from employees;");
16 if(PQresultStatus(res) != PGRES_TUPLES_OK) {
17 fprintf(stderr,"Query failed: %s\n",PQresultErrorMessage(res));
18 exit(1);
19 }
20
21 for(i=0;i<PQntuples(res);i++) {
22 for(j=0;j<PQnfields(res);j++) {
23 printf("%s: %s ",PQfname(res,j),PQgetvalue(res,i,j));
24 }
25 printf("\n");
26 }
27 PQclear(res);
28 PQfinish(conn);
29 return(0);
30 }
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