sql alter column null

However, Microsoft SQL server has an important defect in processing such indexes, that is, the operations that should have been compiled into index seek are compiled into index scanning, which may cause serious performance degradation. For example, assume that a table T has an index (cityid, sentdate, userid) and now has a paging list function, to query several records greater than a certain multi-Column C

[Mysql] The SQL _mode configuration associated with Data truncated for column, truncatedsql_mode System Logs Ata truncated for column 'agent' at row 1 The reason for this problem in mysql is nothing more than Character Set setting or a too long field.Mysql has been unified into UTF-8 during initialization, so you can ignore this problem. If the string is too lon

Concatenate multiple rows of records in the same column in Oracle into a string [SQL] -- raw data -- a 111 -- B 222 -- a 333 -- a 444 -- B 555 -- final result -- a 111*333*444 SELECT L4.L _ TIME, MAX (SUBSTR (L4. group CONTENT, 2) final field value FROM (SELECT L3.L _ TIME, SYS_CONNECT_BY_PATH (L3.L _ CONTENT ,'*') AS group content from (SELECT L2.L _ TIME, L2.L _ CONTENT, L2.L _ TIME | L2. group id as grou

When using a stored procedure, you can use dynamic SQL when dynamically passing the table name or column name.CodeAs follows; Alter procedure proc_updatedatetimecounter @ Businessnum nvarchar ( 200 ), -- Business number @ Column nvarchar ( 200 ), -- Column name @ Value

. Extended_properties. VALUE fromsyscolumnsINNER JOINSYS. Extended_properties onSyscolumns.id=SYS. Extended_properties. major_id andsyscolumns. COLID=SYS. Extended_properties. minor_idINNER JOINSYSOBJECTS onSyscolumns.id=sysobjects.idWHERESysobjects.name=So.name andSyscolumns.name=Sc.name) Description--So . Name Table name, SC. Name Column name fromSYS. COLUMNS Sc,sys. TYPES St,sys. SYSOBJECTS so--Column na

Because in the SQL-SERVER, the auto-incrementing column property cannot be directly modified, but you can achieve it through the following method: 1. If you only insert a specified value, use the following statement to temporarily cancel the operation. Set identity_insert tablename onInsert into tablename (XX, XX) values (XX, XX)Set identity_insert tablename off 2. Add a

'))Drop function [dbo]. [function name]7 getting user-created object informationSELECT [name],[id],crdate from sysobjects where xtype= ' U '8 determining whether a column existsif exists (SELECT * from syscolumns where id=object_id (' table name ') and name= ' column name ')ALTER TABLE table name drop column name9 Jud

Introduction T-SQL is not just a language for querying a database, or a language that can manipulate data. Column-based case expressions are one of them, unlike other query statements that can be substituted for each other (for example, queries implemented with subqueries can also be implemented by joins), and case expressions are largely irreplaceable in the control of columns based logic. The case expres

Grammar:Pivot is used to rotate column values to column names (row to column), which can be implemented in SQL Server in conjunction with a case statement with an aggregate function the general syntax for pivot is:pivot( aggregate function (column) for

Auto-increment column: [PID] [int] IDENTITY (1, 1) NOT NULLSet the primary key: The PK_t_LockDataNet prefix pk_is hard to understand.Alter table hyoa_SysInfo .. t_LockDataNet ADD CONSTRAINTPK_t_LockDataNet PRIMARY KEY CLUSTERED(PID) ON [PRIMARY];Set the default value: DF_t_LockDataNet_TotalNum prefix DF _ TABLE name_field nameAlter table hyoa_SysInfo .. t_LockDataNet ADDCONSTRAINT [DF_t_LockDataNet_TotalNum] DEFAULT (5) FOR [TotalNum],CONSTRAINT [DF_t

How to determine the maximum value in the SQL Server Column Create table [dbo]. [MinMax] ( [MinMaxID] [int] IDENTITY (1, 1) not null, [Value1] [int] NULL, [Value2] [int] NULL, [Value3] [int] NULL, [Value4] [int]

A simple SQL row and column conversion Author:eaglet In database development, we often encounter the problem of row and column conversion, such as the following question, department, employee and employee type three sheets, we want to count similar list Department Number department name total formal staff temporary staff dismiss staff 1 A 30 20 10 1 This problem

adding the course. And the third one doesn't have that kind of problem. Note: MySQL cannot remove another stored procedure in one stored procedure, only another stored procedure can be calledOriginally wanted to write in method three: DROP PROCEDURE IF EXISTS sp_count (); This is wrong. Debugging when the wrong write, can only be manually deleted, and did not find a good method. References: Relive sql--row to