关于表中的字段数量

Oracle9i Database Reference Release 2 (9.2)，里面第四章Database Limits的Logical Database Limits一节讲到了，答案是每表最大1000列。现摘录如下：
Logical Database Limits
Item……项目
Type……类型
Limit ……限制

GROUP BY clause
Maximum length
The GROUP BY expression and all of the nondistinct aggregate functions (for example, SUM, AVG) must fit within a single database block.

Indexes
Maximum per table
Unlimited

total size of indexed column
75% of the database block size minus some overhead

Columns
Per table
1000 columns maximum

Per index (or clustered index)
32 columns maximum

Per bitmapped index
30 columns maximum


Constraints
Maximum per column
Unlimited

Subqueries
Maximum levels of subqueries in a SQL statement
Unlimited in the FROM clause of the top-level query

255 subqueries in the WHERE clause

Partitions
Maximum length of linear partitioning key
4 KB - overhead

Maximum number of columns in partition key
16 columns

Maximum number of partitions allowed per table or index
64 K-1 partitions

Rollback Segments
Maximum number per database
No limit; limited within a session by the MAX_ROLLBACK_SEGMENTS initialization parameter

Rows
Maximum number per table
Unlimited

SQL Statement Length
Maximum length of statements
64 K maximum; particular tools may impose lower limits

Stored Packages
Maximum size
PL/SQL and Developer/2000 may have limits on the size of stored procedures they can call. The limits typically range from 2000 to 3000 lines of code.

See Also: Your PL/SQL or Developer/2000 documentation for details

Trigger Cascade Limit
Maximum value
Operating system-dependent, typically 32

Users and Roles
Maximum
2,147,483,638

Tables
Maximum per clustered table
32 tables

Maximum per database
Unlimited