多种数据库查询数据表是否存在_若依判断表存在-优快云博客

本文介绍了一个用于检查不同数据库环境中指定表是否存在的通用函数。该函数通过动态构造SQL查询来适应多种数据库系统，如IBM DB2、MySQL、Oracle、PostgreSQL和SQLite。每种数据库系统都有特定的查询语法。

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int	DBtable_exists(const char *table_name)
{
	char		*table_name_esc;
#ifdef HAVE_POSTGRESQL
	char		*table_schema_esc;
#endif
	DB_RESULT	result;
	int		ret;

	table_name_esc = DBdyn_escape_string(table_name);

#if defined(HAVE_IBM_DB2)
	/* publib.boulder.ibm.com/infocenter/db2luw/v9r7/topic/com.ibm.db2.luw.admin.cmd.doc/doc/r0001967.html */
	result = DBselect(
			"select 1"
			" from syscat.tables"
			" where tabschema=user"
				" and lower(tabname)='%s'",
			table_name_esc);
#elif defined(HAVE_MYSQL)
	result = DBselect("show tables like '%s'", table_name_esc);
#elif defined(HAVE_ORACLE)
	result = DBselect(
			"select 1"
			" from tab"
			" where tabtype='TABLE'"
				" and lower(tname)='%s'",
			table_name_esc);
#elif defined(HAVE_POSTGRESQL)
	table_schema_esc = DBdyn_escape_string(NULL == CONFIG_DBSCHEMA || '\0' == *CONFIG_DBSCHEMA ?
			"public" : CONFIG_DBSCHEMA);

	result = DBselect(
			"select 1"
			" from information_schema.tables"
			" where table_name='%s'"
				" and table_schema='%s'",
			table_name_esc, table_schema_esc);

	zbx_free(table_schema_esc);

#elif defined(HAVE_SQLITE3)
	result = DBselect(
			"select 1"
			" from sqlite_master"
			" where tbl_name='%s'"
				" and type='table'",
			table_name_esc);
#endif

	zbx_free(table_name_esc);

	ret = (NULL == DBfetch(result) ? FAIL : SUCCEED);

	DBfree_result(result);

	return ret;
}