“已删除的行”数据库中的指标？ [英] the "deleted row" indicator in dbase?
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问题描述
您知道没有dBase的x64驱动程序。
http://msdn.microsoft.com/zh-cn/vfoxpro/bb190289.aspx
我试图做一个。
是比ODBC快得多。但是只有一个问题。
我无法确定是否删除了行。
As you know there is no x64 driver for dBase.
"http://msdn.microsoft.com/en-us/vfoxpro/bb190289.aspx"
I tried to make one.
It is extremely faster than ODBC.but there is only one problem.
I cannot determine if a row is deleted or not.
推荐答案
每个记录的第一个字节（不是标题或字段描述，而是实际的记录数据）将包含星号（ *
The first byte of each record (not header or field description, but actual record data) will contain an asterisk ("*") if the record is deleted, or a blank space (" ") if not.
以下是我在Wotsit.org上找到的内容，可能对您有所帮助：
Here's something I found a while back on Wotsit.org that may help:
----------------------------------------------------------------------------
Genaral Format of .dbf files in Xbase languages 18-Nov-96
----------------------------------------------------------------------------
Applies for / supported by:
FS = FlagShip D3 = dBaseIII+
Fb = FoxBase D4 = dBaseIV
Fp = FoxPro D5 = dBaseV
CL = Clipper
1. DBF Structure
================
Byte Description
------+--------------------------------------
0..n .dbf header (see 2 for size, byte 8)
n+1 1st record of fixed length (see 2&3) \
2nd record (see 2 for size, byte 10) \ if dbf is
... / not empty
last record /
last optional: 0x1a (eof byte)
2. DBF Header (variable size, depending on field count)
=======================================================
Byte Size Contents Description Applies for (supported by)
----+----+--------+----------------------------+-----------------------------
00 1 0x03 plain .dbf FS, D3, D4, D5, Fb, Fp, CL
0x04 plain .dbf D4, D5 (FS)
0x05 plain .dbf D5, Fp (FS)
0x43 with .dbv memo var size FS
0xB3 with .dbv and .dbt memo FS
0x83 with .dbt memo FS, D3, D4, D5, Fb, Fp, CL
0x8B with .dbt memo in D4 format D4, D5
0x8E with SQL table D4, D5
0xF5 with .fmp memo Fp
01 3 YYMMDD Last update digits all
04 4 ulong Number of records in file all
08 2 ushort Header size in bytes all
10 2 ushort Record size in bytes all
12 2 0,0 Reserved all
14 1 0x01 Begin transaction D4, D5
0x00 End Transaction D4, D5
0x00 ignored FS, D3, Fb, Fp, CL
15 1 0x01 Encryptpted D4, D5
0x00 normal visible all
16 12 0 (1) multi-user environment use D4,D5
28 1 0x01 production index exists Fp, D4, D5
0x00 index upon demand all
29 1 n language driver ID D4, D5
0x01 codepage 437 DOS USA Fp
0x02 codepage 850 DOS Multi ling Fp
0x03 codepage 1251 Windows ANSI Fp
0xC8 codepage 1250 Windows EE Fp
0x00 ignored FS, D3, Fb, Fp, CL
30 2 0,0 reserved all
32 n*32 Field Descriptor, see (2a) all
+1 1 0x0D Header Record Terminator all
2a. Field descriptor array in dbf header (fix 32 bytes for each field)
========================================
Byte Size Contents Description Applies for (supported by)
----+----+--------+----------------------------+-----------------------------
0 11 ASCI field name, 0x00 termin. all
11 1 ASCI field type (see 2b) all
12 4 n,n,n,n fld address in memory D3
n,n,0,0 offset from record begin Fp
0,0,0,0 ignored FS, D4, D5, Fb, CL
16 1 byte Field length, bin (see 2b) all \ FS,CL: for C field type,
17 1 byte decimal count, bin all / both used for fld lng
18 2 0,0 reserved all
20 1 byte Work area ID D4, D5
0x00 unused FS, D3, Fb, Fp, CL
21 2 n,n multi-user dBase D3, D4, D5
0,0 ignored FS, Fb, Fp, CL
23 1 0x01 Set Fields D3, D4, D5
0x00 ignored FS, Fb, Fp, CL
24 7 0..0 reserved all
31 1 0x01 Field is in .mdx index D4, D5
0x00 ignored FS, D3, Fb, Fp, CL
2b. Field type and size in dbf header, field descriptor (1 byte)
=======================================================
Size Type Description/Storage Applies for (supported by)
------+---------+------------------------------+-----------------------------
C 1..n Char ASCII (OEM code page chars) all
rest= space, not \0 term.
n = 1..64kb (using deci count) FS
n = 1..32kb (using deci count) Fp, CL
n = 1..254 all
D 8 Date 8 Ascii digits (0..9) in the all
YYYYMMDD format
F 1..n Numeric Ascii digits (-.0123456789) FS, D4, D5, Fp
variable pos. of float.point
n = 1..20
N 1..n Numeric Ascii digits (-.0123456789) all
fix posit/no float.point
n = 1..20 FS, Fp, CL
n = 1..18 D3, D4, D5, Fb
L 1 Logical Ascii chars (YyNnTtFf space) FS, D3, Fb, Fp, CL
Ascii chars (YyNnTtFf ?) D4, D5 (FS)
M 10 Memo 10 digits repres. the start all
block posit. in .dbt file, or
10spaces if no entry in memo
V 10 Variable Variable, bin/asc data in .dbv FS
4bytes bin= start pos in memo
4bytes bin= block size
1byte = subtype
1byte = reserved (0x1a)
10spaces if no entry in .dbv
P 10 Picture binary data in .ftp Fp
structure like M
B 10 Binary binary data in .dbt D5
structure like M
G 10 General OLE objects D5, Fp
structure like M
2 2 short int binary int max +/- 32767 FS
4 4 long int binary int max +/- 2147483647 FS
8 8 double binary signed double IEEE FS
3. Each Dbf record (fix length)
==================
Byte Size Description Applies for (supported by)
------+----+--------------------------------------+--------------------------
0 1 deleted flag "*" or not deleted " " all
1..n 1.. x-times contents of fields, fixed all
length, unterminated.
For n, see (2) byte 10..11
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