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This article mainly explains the "data structure of MySQL database operation results". The content of the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn the data structure of MySQL database operation results.

I. data structure of database operation results

Struct zbx_db_result

{

# if defined (HAVE_IBM_DB2)

SQLHANDLE hstmt

SQLSMALLINT nalloc

SQLSMALLINT ncolumn

DB_ROW values

DB_ROW values_cli

SQLINTEGER * values_len

# elif defined (HAVE_MYSQL)

MYSQL_RES * result

# elif defined (HAVE_ORACLE)

OCIStmt * stmthp; / * the statement handle for select operations * /

Int ncolumn

DB_ROW values

Ub4 * values_alloc

OCILobLocator * * clobs

# elif defined (HAVE_POSTGRESQL)

PGresult * pg_result

Int row_num

Int fld_num

Int cursor

DB_ROW values

# elif defined (HAVE_SQLITE3)

Int curow

Char * * data

Int nrow

Int ncolumn

DB_ROW values

# endif

}

The database is queried according to sql

/ *

* *

* Function: DBselect *

* *

* Purpose: execute a select statement *

* *

* Comments: retry until DB is up *

* *

* * /

DB_RESULT _ _ zbx_DBselect (const char * fmt,...)

{

Va_list args; / / Parameter list

DB_RESULT rc

Va_start (args, fmt)

Rc = zbx_db_vselect (fmt, args)

While ((DB_RESULT) ZBX_DB_DOWN = = rc)

{

DBclose ()

DBconnect (ZBX_DB_CONNECT_NORMAL)

If ((DB_RESULT) ZBX_DB_DOWN = (rc = zbx_db_vselect (fmt, args)

{

Zabbix_log (LOG_LEVEL_ERR, "database is down: retrying in% d seconds", ZBX_DB_WAIT_DOWN)

Connection_failure = 1

Sleep (ZBX_DB_WAIT_DOWN)

}

}

Va_end (args)

Return rc

}

3. Data structure of MySQL operation result

Typedef struct st_mysql_res {

My_ulonglong row_count

MYSQL_FIELD * fields

MYSQL_DATA * data

MYSQL_ROWS * data_cursor

Unsigned long * lengths; / * column lengths of current row * /

MYSQL * handle; / * for unbuffered reads * /

Const struct st_mysql_methods * methods

MYSQL_ROW row; / * If unbuffered read * /

MYSQL_ROW current_row; / * buffer to current row * /

MEM_ROOT field_alloc

Unsigned int field_count, current_field

My_bool eof; / * Used by mysql_fetch_row * /

/ * mysql_stmt_close () had to cancel this result * /

My_bool unbuffered_fetch_cancelled

Void * extension

} MYSQL_RES

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