修改OracleXE管理界面端口
2014年8月19日 12:54
OracleXE管理界面默认端口是8080，修改方法：进入OracleXE命令行界面，执行以下命令
1 2 3 4 | SQL> connect / as sysdba已连接。SQL> exec dbms_xdb.sethttpport(8081);PL/SQL过程已成功完成。 |
sqlfront.h 没有那个文件或目录
2014年4月23日 17:12
- 安装pymssql，出现下面情况
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 | [wyq@localhost ~]$ sudo pip install pymssqlDownloading/unpacking pymssql Downloading pymssql-2.1.0.tar.bz2 (1.9MB): 0% 8.2kB Downloading pymssql-2.1.0.tar.bz2 (1.9MB): 1.9MB downloaded Running setup.py egg_info for package pymssql setup.py: platform.system() => 'Linux' setup.py: platform.architecture() => ('64bit', 'ELF') setup.py: platform.linux_distribution() => ('Fedora', '20', 'Heisenbug') setup.py: platform.libc_ver() => ('glibc', '2.2.5') setup.py: Not using bundled FreeTDS setup.py: include_dirs = ['/usr/local/include'] setup.py: library_dirs = ['/usr/local/lib'] warning: no files found matching 'pymssql_version.py' warning: no files found matching 'win32/freetds.zip' warning: no previously-included files matching '*' found under directory 'docs/_build'Installing collected packages: pymssql Running setup.py install for pymssql setup.py: platform.system() => 'Linux' setup.py: platform.architecture() => ('64bit', 'ELF') setup.py: platform.linux_distribution() => ('Fedora', '20', 'Heisenbug') setup.py: platform.libc_ver() => ('glibc', '2.2.5') setup.py: Not using bundled FreeTDS setup.py: include_dirs = ['/usr/local/include'] setup.py: library_dirs = ['/usr/local/lib'] building '_mssql' extension gcc -pthread -fno-strict-aliasing -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -D_GNU_SOURCE -fPIC -fwrapv -DNDEBUG -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -D_GNU_SOURCE -fPIC -fwrapv -fPIC -I/usr/local/include -I/usr/include/python2.7 -c _mssql.c -o build/temp.linux-x86_64-2.7/_mssql.o -DMSDBLIB _mssql.c:346:22: 致命错误：sqlfront.h：没有那个文件或目录 #include "sqlfront.h" ^ 编译中断。 error: command 'gcc' failed with exit status 1 Complete output from command /usr/bin/python -c "import setuptools;__file__='/tmp/pip_build_root/pymssql/setup.py';exec(compile(open(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-K_4vEY-record/install-record.txt --single-version-externally-managed: setup.py: platform.system() => 'Linux'setup.py: platform.architecture() => ('64bit', 'ELF')setup.py: platform.linux_distribution() => ('Fedora', '20', 'Heisenbug')setup.py: platform.libc_ver() => ('glibc', '2.2.5')setup.py: Not using bundled FreeTDSsetup.py: include_dirs = ['/usr/local/include']setup.py: library_dirs = ['/usr/local/lib']running installrunning buildrunning build_extbuilding '_mssql' extensioncreating buildcreating build/temp.linux-x86_64-2.7gcc -pthread -fno-strict-aliasing -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -D_GNU_SOURCE -fPIC -fwrapv -DNDEBUG -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -D_GNU_SOURCE -fPIC -fwrapv -fPIC -I/usr/local/include -I/usr/include/python2.7 -c _mssql.c -o build/temp.linux-x86_64-2.7/_mssql.o -DMSDBLIB_mssql.c:346:22: 致命错误：sqlfront.h：没有那个文件或目录 #include "sqlfront.h" ^编译中断。error: command 'gcc' failed with exit status 1----------------------------------------Cleaning up...Command /usr/bin/python -c "import setuptools;__file__='/tmp/pip_build_root/pymssql/setup.py';exec(compile(open(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-K_4vEY-record/install-record.txt --single-version-externally-managed failed with error code 1 in /tmp/pip_build_root/pymssqlTraceback (most recent call last): File "/bin/pip", line 9, in <module> load_entry_point('pip==1.4.1', 'console_scripts', 'pip')() File "/usr/lib/python2.7/site-packages/pip/__init__.py", line 147, in main return command.main(args[1:], options) File "/usr/lib/python2.7/site-packages/pip/basecommand.py", line 169, in main text = '\n'.join(complete_log)UnicodeDecodeError: 'ascii' codec can't decode byte 0xe8 in position 21: ordinal not in range(128) |
- 需要安装freetds
1 | sudo yum install freetds-devel |
SQLServer和Sybase使用的协议是TDS协议，linux中使用freetds连接SQLServer.
SQL标准规定中null值判断是否合理？
2014年2月11日 18:50
在postgres中判断null值时，下面语句的结果不相等，为什么？
1 2 | select * from user_info where user_name is nullselect * from user_info where user_name = null |
原因是postgres遵循sql标准，在ANSI SQL(SQL-92)标准中规定的Null值的比较取值结果都为False.
它认为NULL 代表一个未知的数值，无法知道两个未知的数值是否相等。
这个理由很不充分，既然无法判断，那么is null又是如何判断它是空的呢?
虽然null表面含义是未知值，但是计算机中不可能有不确定的表示. 常见程序语言中null实际都是一个特殊值，一个确定的特殊值。所以在编程语言中是允许使用null=null(值比较)的. SQL中不允许是否合理?
