sql not null constraint

This is a question that is often asked. In particular, when using Oracle, the client would have a problem with SQL Server, which is that SQL Server behaves differently from Oracle on top of NULL values. In Oracle, a null value is considered to be an infinity value, so if you arrange it in ascending order, it will be r

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 > 0Okay, so you don't have to

Label:Today in writing a refund of the SQL encountered a problem, directly resulting in the previous record of all operations log, emptied, fortunately, I have to look at the data habits, the following code 1UPDATE Tradeuser 2 set 3 userscore= @UserScore 4 remark=isnull ( Remark,+" ' After the execution of this SQL, the comments are emptied directly, the solution can not find the reason. In fact, the re

Tags: src log val Student technology share aggregate function personal insert upper As we all know, aggregate functions are statistical, and the Count function is the number of rows, that is, the number of rows that satisfy a certain condition. Let's look at this subtle relationship between count and null. CREATE TABLE dbo. Student (Snoint NULL, Name nvarchar ( at) ) INSERT into dbo. Student (Sno,name) VAL

There are the following inquiries: Copy Code code as follows: Select IsNull (lastchanged, ') as lastchanged from vhhostlist where s_comment= ' test202 ' Originally, the ISNULL function has only one argument, which means to determine whether the value of this parameter is NULL, is NULL to return True, otherwise return false; However, in SQL

A B c D 980515 Jing Top Enterprise Co., Ltd. simple home Hao NULL 980514 full Hin Wood Industry Co., Ltd. NULL 123 980514 Xun billion Technology Co., Ltd. Simple and NULL 980515 San Yue International Enterprise Co., Ltd NULL 111 Table structure as shown above, the SQL

Recently done a small test site, where there is a page, the page load need to calculate a number ofThere is a row of SQL statements,Select SUM (FileSize) from [File] where [email protected], everything is OK during native testingBut did not expect is because of this sentence SQL statement, tossing the afternoon, the machine vs2012+sqlserver2008When you deploy to the server, you always get an error when you

Tags: mybatis sql MySQL Web development inNot rigorous writing, may be error: in (), this situation does not conform to the MySQL syntax.Select from Loanwhere loan_id in#{item}Either in a MyBatis SQL file or in a Java program.the syntax in SQL :SELECT *From p2p_loan_variation where 1 = 1and loan_id inSeparator= "," close= ")" >#{item}What to do in Java:list if (L

There are two T-SQL below, at first glance thought to be equivalent, but actually not select orderid1, Localcost, Supplygoodsname, Buyersgoodsid, Jsitid, Gsitid from csc_ Result with (NOLOCK) where [level ] > 0 and orderid1 like ' 618464266 % ' and (supplygoodsid Not in (1085317 , 1112957 )) SELECTORDERID1, Localcost, Supplygoodsname, Buyersgoodsid, Jsitid, G

Tags: span sel rom PAC record padding statement size SQLWhen writing SQL conditional statements is often used not equal to ' Example: Table A A1 B1 1 0 2 1 3 Null The result of querying with SELECT * from A where b1 A1 B1 1 0 The third column B1 is empty and w

Tags: War limit warning EOF get color style aggregation divThis warning has no effect in a regular scenario, but if you run SQL with Excel, it will prevent you from succeeding with this warning ~ In fact, Excel does a lot of SQL restrictions and needs more artifice, and I wrote one before. To deal with this warning, one of course is to add isnull to the place where the aggregate function is used in the stat

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