在Oracle中若删除一个不存在的表,如 “DROP TABLE tableName”,则会提示:
ORA-00942:表或视图不存在
若在程序中执行该语句则会报异常,这就需要我们在删除表前先判断该表是否存在,若存在则删除.
DECLARE
num NUMBER;
BEGIN
SELECT COUNT(1)
INTO num
FROM USER_TABLES
WHERE TABLE_NAME = UPPER('tableName');
IF num > 0 THEN
EXECUTE IMMEDIATE 'DROP TABLE tableName';
END IF;
END;
在Oracle中若删除表中一个不存在的字段,如 “alter table test drop column xxx”,则会提示:
ORA-00904:”xxx”:标识符无效
若在程序中执行该语句则会报异常,这就需要我们在删除字段前先判断该字段是否存在,若存在则删除.
DECLARE
num NUMBER;
BEGIN
SELECT COUNT(1)
INTO num
from cols
where table_name = upper('tableName')
and column_name = upper('columnName');
IF num > 0 THEN
execute immediate 'alter table tableName drop column columnName';
END IF;
END;