sql not null constraint

Label:Sum is the standard SUM function in an SQL statement, and the SUM function returns null if there are no records that match the criteria. But in most cases, we want it to return 0 instead of NULL if the condition record is not met, so we can use the following method, for example: SELECT COALESCE (SUM (name), 0) from the person WHERE ID > 0 Okay, so you don'

Label:DECLARE @code varchar, @cs varchar, @zc varchar (20)Set @cs = ' (' [email protected]+ ' * ' [email protected]+ ') 'print ' character ' [email protected]INSERT into TESTER2 values (@cs, @zc, @cs)DECLARE @code varchar, @cs varchar, @zc varchar (20)Set @cs = ' 1 'Set @zc = ' 2 'Set @cs = ' (' [email protected]+ ' * ' [email protected]+ ') 'print ' character ' [email protected]INSERT into TESTER2 values (@cs, @zc, @cs)In the above two pieces of code, the first code may be unable to execute the

IamlaosongSQL query statement using% to do fuzzy query, the program generally requires users to enter some information, based on this information fuzzy query. For example, user input 340104, the following statement is to query yesterday customer code 340104 beginning with all the message information:SELECT * from tb_evt_mail_clct t where t.clct_date = Trunc (sysdate-1) and t.sender_cust_code like ' 340,104% 'When the user does not enter anything need to query yesterday all the message informa

We often encounter null in the use or maintenance of SQL Server, so what is NULL? The following is a short description from MSDN (see "Null Values"): A value of NULL indicates that's the value is unknown. A value of NULL is

A lot of people have this problem. What is the difference between populating a null value in SQL and NULLNow I'm going to share your thoughts with an example. Please give us your criticism and correct me.Create a Time tableCREATE TABLE #temp (name VARCHAR (50))Fill three information as follows:INSERT into #tempVALUES (NULL)INSERT into #tempVALUES (' Tom ')INSERT

Copy codeThe Code is as follows:-determines whether some fields are empty. -- Case Select case when 'field name' is null then' \ n' else convert (varchar (20), 'field name') end as 'newname' Select case when null is null then' \ n' else convert (varchar (20), null) end as 'newname' --

Label:Recently encountered a more interesting problem in the project, the online search for some methods, summarized here to share. We often encounter such a scenario: the need to query data, there are some query conditions, but when the query, we hope that when a condition is empty, then do not filter this condition, the main idea is to deal with the following: 1, the program collects query query condition processing, this suitable for dynamic SQL, s

PublicListgetAll1 (Stringname) throwsException {ListresultnewArrayList (); ConnectionconDatabaseConnection. getConnection (); Stringnanull; Stringsql1 quot; select * fromguanzhuwhereguanzhu? Quot; PreparedStatementps1con. prepareS java database mysql computer jsp Public ListgetAll1 (String name) throws Exception {Listresult = new ArrayList ();Connection con = DatabaseConnection. getConnection ();String na = null;String sql1 = "select * from gua

Recently compiled Asp.net in vs2008ProgramWhen connecting to the database, the following error occurs: Login Failed for user' (null) '. Reason: not associated with a trusted SQL server connection. My connection string is: conn. connectionstring = "Server = pc-201007021400 \ WinCC; uid =; Pwd =; database =" filename It seems that uid has an error, and then changed to: conn. connectionstring = "Server =

How does php determine whether the query result of an SQL statement is null? The code is as follows: $ SQL nbsp; = mysql_query ( nbsp; "select nbsp; * nbsp; from nbsp; TV _video nbsp; where nbsp; title nbsp; how does like nb php determine whether the SQL statement query result is

Method 1:When the publisher filter condition is NULL, how do you write SQL?1 DECLARE @publishers VARCHAR (50);2 SELECT * FROM dbo. Book WHERE Publishers=isnull (@publishers, publishers)Method 2:DECLARE @cinv varchar (50)SELECT * from inventory where 1=1 and ([email protected] or @cinv is null)Method 3:DECLARE @name VARCHAR (+), @page INT =1SET @name = ' Zhang San

Sql ISNULL() 函数 使用指定的替换值替换 NULL。语法ISNULL( check_expression , replacement_value ) 参数check_expression将被检查是否为 NULL的表达式。check_expression 可以是任何类型的。replacement_value 在 check_expression 为 NULL时将返回的表达式。replacement_value 必须与 check_expresssion 具有相同的类型。返回类型返回与 check_expression 相同的类型。注释如果 check_expression 不为

SQL ISNULL (), NVL (), Ifnull (), and COALESCE () functionsTake a look at the "Products" table below: p_id ProductName UnitPrice UnitsInStock UnitsOnOrder 1 Computer 699 25 15 2 Printer 365 36 3 Telephone 280 159 57 If "UnitsOnOrder" is optional, and can contain N