1. sql语句（mysql）怎么去掉字段内一部分内容
可以使用字符串处理函数来去掉字段的不分内容，例如insert(),replace()等等函数也可以组合使用它们。
例如下面的例子用这两个函数分别用零长度字符串将字段C中第二个字符开始长度为2的字符去掉，以及将字段C中所有的字符“cd”清除掉：
select c,
insert(c,2,2,''),
replace(c,'cd','') from example;
2. sql 删除语句
1、delete 语句用于删除表中的行。delete语句执行删除的过程是每次从表中删除一行，并且同时将该行的删除操作作为事务记录在日志中保存
语法：DELETE FROM 表名称 WHERE 列名称 = 值，
如：删除student表中姓名为张三丰的学生信息-delete from studentwhere name=‘张三丰’；
2、drop (删除表)：删除内容和定义，释放空间。简单来说就是把整个表去掉.以后要新增数据是不可能的,除非新增一个表。
drop语句将删除表的结构被依赖的约束（constrain),触发器（trigger)索引（index);依赖于该表的存储过程/函数将被保留，但其状态会变为：invalid。
3、truncate (清空表中的数据)：删除内容、释放空间但不删除定义(保留表的数据结构)。与drop不同的是,只是清空表数据而已。
注意:truncate 不能删除行数据,要删就要把表清空。
(2)sql语句去掉零扩展阅读：
数据库操作中，经常要用到删除表和删除表数据，在实际应用中，三者的区别是明确的。
当你不再需要该表时， 用 drop;
当你仍要保留该表，但要删除所有记录时， 用 truncate;
当你要删除部分记录时（always with a WHERE clause), 用 delete。
truncate 与delete 比较：
1、truncate table 在功能上与不带 WHERE 子句的 delete语句相同：二者均删除表中的全部行。
2、truncate 比 delete速度快，且使用的系统和事务日志资源少。
3、truncate 操作后的表比Delete操作后的表要快得多。
3. SQL语句 Decimal如何去掉末尾无用的0
用round函数
select round(A,2) FROM [表名]
round(A,2)中的2表示取小数点后两位,取3位就写3,依此类推
4. SQL清除语句
CREATE SNAPSHOT [schema.]snapshot
[ [PCTFREE integer] [PCTUSED integer]
[INITRANS integer] [MAXTRANS integer]
[TABLESPACE tablespace]
[STORAGE storage_clause]
[ USING INDEX [ PCTFREE integer | TABLESPACE tablespace
| INITTRANS integer | MAXTRANS integer
| STORAGE storage_clause ] ...
| [CLUSTER cluster (column [, column]...)] ]
[ REFRESH [FAST | COMPLETE | FORCE] [START WITH date] [NEXT date]]
AS subquery
schema
is the schema to contain the snapshot. If you omit schema, Oracle
creates the snapshot in your schema.
snapshot
is the name of the snapshot to be created.
Oracle chooses names for the table, views, and index used to
maintain the snapshot by prefixing the snapshot name. To limit
these names to 30 bytes and allow them to contain the entire
snapshot name, Oracle Corporation recommends that you limit your
snapshot names to 23 bytes.
PCTFREE
PCTUSED
INITRANS
MAXTRANS
establishes values for these parameters for the internal table
Oracle uses to maintain the snapshot's data.
TABLESPACE
specifies the tablespace in which the snapshot is to be created. If
you omit this option, Oracle creates the snapshot in the default
tablespace of the owner of the snapshot's schema.
STORAGE
establishes storage characteristics for the table Oracle uses to
maintain the snapshot's data.
USING INDEX
specifies the storage characteristics for the index on a simple
snapshot. If the USING INDEX clause not specified, the index is
create with the same tablespace and storage parameters as the
snapshot.
CLUSTER
creates the snapshot as part of the specified cluster. Since a
clustered snapshot uses the cluster's space allocation, do not use
the PCTFREE, PCTUSED, INITRANS, or MAXTRANS parameters, the
TABLESPACE option, or the STORAGE clause in conjunction with the
CLUSTER option.
REFRESH
specifies how and when Oracle automatically refreshes the snapshot:
FAST
specifies a fast refresh, or a refresh using only the
updated data stored in the snapshot log associated
with the master table.
COMPLETE
specifies a complete refresh, or a refresh that re-
executes the snapshot's query.
FORCE
specifies a fast refresh if one is possible or
complete refresh if a fast refresh is not possible.
Oracle decides whether a fast refresh is possible at
refresh time.
If you omit the FAST, COMPLETE, and FORCE options,
Oracle uses FORCE by default.
START WITH
specifies a date expression for the first automatic
refresh time.
NEXT
specifies a date expression for calculating the
interval between automatic refreshes.
Both the START WITH and NEXT values must evaluate to a time in the
future. If you omit the START WITH value, Oracle determines the
first automatic refresh time by evaluating the NEXT expression when
you create the snapshot. If you specify a START WITH value but omit
the NEXT value, Oracle refreshes the snapshot only once. If you
omit both the START WITH and NEXT values or if you omit the REFRESH
clause entirely, Oracle does not automatically refresh the snapshot.
AS subquery
specifies the snapshot query. When you create the snapshot, Oracle
executes this query and places the results in the snapshot. The
select list can contain up to 253 expressions. A snapshot query is
subject to the same restrictions as a view query.
PREREQUISITES:
To create a snapshot in your own schema, you must have CREATE
SNAPSHOT system privilege. To create a snapshot in another user's
schema, you must have CREATE ANY SNAPSHOT system privilege.
Before a snapshot can be created, the user SYS must run the SQL
script DBMSSNAP.SQL on both the database to contain the snapshot and
the database(s) containing the tables and views of the snapshot's
query. This script creates the package SNAPSHOT which contains both
public and private stored proceres used for refreshing the
snapshot and purging the snapshot log. The exact name and location
of this script may vary depending on your operating system.
When you create a snapshot, Oracle creates a table, two views, and
an index in the schema of the snapshot. Oracle uses these objects
to maintain the snapshot's data. You must have the privileges
necessary to create these objects. For information on these
privileges, see the CREATE TABLE, CREATE VIEW, and CREATE INDEX
commands.
The owner of the schema containing the snapshot must have either
space quota on the tablespace to contain the snapshot or UNLIMITED
TABLESPACE system privilege. Also, both you (the creator) and the
owner must also have the privileges necessary to issue the
snapshot's query.
To create a snapshot, you must be using Oracle with the proceral
option. To create a snapshot on a remote table or view, you must
also be using the distributed option.
5. sql语句 怎么去掉小数点后多余的 0
declare @s numeric(20,10)
set @s = 2555.784000
select
case when cast(@s as float) > cast(cast(@s as float) as INT)
then cast(@s as float)
else cast(cast(@s as float) as int)
end
6. sql语句去掉前面一个零谢谢了，大神帮忙啊
这个字段是定长的还是不定长的？ 定长的就 select substring(列名,2,3) from table 就行了 不定长的话可以建一个函数做，到时候可以追问
7. sql语句如何去掉没有值的
你具体想实现什么功能啊？如果就是筛选记录的话就是楼上说的那样。
8. 求sql语句数据里有0001，0010，0101如何只去掉1前边的0
可以先转换成int型，再换回varchar就可以
select convert(varchar(4),convert(int,'0001'))
9. 怎么在sql语句中将月和日中前面的0去掉，比如09月07日，我只有9月7日
selectto_char(to_char(to_date(substr(a.rq,0,10),'yyyy-mm-dd'),'m')||'月'||
to_char(to_date(substr(a.rq,0,10),'yyyy-mm-dd'),'d')||'日')rq
fromJW_PKB_ZTJSa
wherea.jsidin(803,804,805,806,807,808)
groupbya.rq
orderbya.rq
10. sql 中输入delete语句为什么提示删除0行
我想是你的逻辑错误。
你把这个触发器，写一下。我帮你看一看