Created
April 26, 2021 12:38
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Attach an user defined function to SQLite database example
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// gcc main.c sqlite3.c -o main.exe | |
#include <stdio.h> | |
#include "sqlite3.h" | |
static void square (sqlite3_context *ctx, int argc, sqlite3_value **argv) { | |
int type = sqlite3_value_type(argv[0]); | |
double d = sqlite3_value_double(argv[0]); | |
switch (type) { | |
case SQLITE_NULL: | |
sqlite3_result_null(ctx); | |
break; | |
case SQLITE_INTEGER: | |
case SQLITE_FLOAT: | |
sqlite3_result_double(ctx, d * d); | |
break; | |
case SQLITE_TEXT: | |
case SQLITE_BLOB: | |
sqlite3_result_error(ctx, "Unsupported", -1); | |
break; | |
default: | |
sqlite3_result_error(ctx, "Impossible", -1); | |
} | |
} | |
int main() { | |
sqlite3* db; | |
if (SQLITE_OK != sqlite3_open_v2(":memory:", &db, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_URI, NULL)) { | |
printf("Error: can't open a database"); | |
return -1; | |
} | |
if (SQLITE_OK != sqlite3_create_function(db, "square", 1, SQLITE_UTF8, 0, square, 0, 0)) { | |
printf("Error: can't register function"); | |
return -1; | |
} | |
sqlite3_stmt* stmt; | |
if (SQLITE_OK == sqlite3_prepare_v2(db, "select ?1, square(?1) union all select ?2, square(?2) union all select ?3, square(?3)", -1, &stmt, 0)) { | |
sqlite3_bind_int(stmt, 1, 5); | |
sqlite3_bind_null(stmt, 2); | |
sqlite3_bind_text(stmt, 3, "abcdef", 6, SQLITE_TRANSIENT); | |
int rc = 0; | |
while (SQLITE_ROW == (rc = sqlite3_step(stmt))) | |
printf("x: %s, square: %s\n", sqlite3_column_text(stmt, 0), sqlite3_column_text(stmt, 1)); | |
if (SQLITE_ERROR == rc) | |
printf(sqlite3_errmsg(db)); | |
} else { | |
printf(sqlite3_errmsg(db)); | |
} | |
sqlite3_finalize(stmt); | |
sqlite3_close_v2(db); | |
return 0; | |
} |
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