oracle sql not null

When using order by for query sorting in Oracle, if there is a null value in the sort field (null), the sort result may not be the result we want. Such as:Sort by the age field in descending order, the result is as follows:Change the SQL statement toSELECT * FROM-Test order BY-age DESC-nulls last;

null and any other value, return unknown because the value of each null is unknown.In this case, how should we compare it with the null value? The answer is to use the isnull function. The isnull function in T-SQL has two parameters, the first parameter is the expression to check whether the expression is

SQL error Description: an error occurs when the OLEDB access interface of the linked server (null) imports data to SQLServer2005. The SQL error description is: linked server (null) the OLEDB access interface STREAM of returns the pair column [! BulkInsert]. The field's Invalid Data rdquo; has been installed with the l

In this series, we mainly introduce the basics of LINQ to SQL. Because of the powerful nature of LINQ, it has different contents for different data sources, this includes the SQL Server database's LINQ to SQL, the XML document's LINQ to XML, and the ADO. NET DataSet;.. NET collections, files, strings, and so on. In addition, some open-source projects that support

You just want to retrieve the records whose Modifier (type VARCHAR2 (20) can be empty) is null from the database table EXPERT_DETAILS, because the field type is VARCHAR2 (20 ), the SQL statement I use is Copy codeThe Code is as follows: select * from expert_details twhere t. modifier ='' No record is retrieved, which is inconsistent with the records stored in the table. Later I thought that even the empty

Problem Description: In processing general data records, for numeric types of fields, in Oracle sort, the null value is the default to be greater than any number of types, of course, for varchar2 type of field, the default is also the processing, but the customer requirements in the process of ordering, Null fields are required to default to the front (small-->)

The ORA-01084 invalid argument in OCI call error is always reported when data is inserted into the Oracle database because one of the field types in the table is CLOB and can be empty when the error is thrown when a null value is inserted into the field. Later, if you decide whether to use DBNull.Value for null values, this resolves the problem.Null refers to an

When Oracle is ordering NULL, desc defaults to the top of the list, ASC defaults to the top, and when sorting is always inconvenient, you need to think about intervening.Method 1: Use the NVL functionThe NVL function can be added after order by for example:ORDER by NVL (Targer_columms, ' 0 ') Method 2: Use nulls first or nulls can be order by after adding nulls first (

When the SELECThellip; INTOhellip; statement is executed in PL_ SQL, if the returned result set is null, The NO_DATA_FOUND error is returned. However, when the SELECT statement has a word When the SELECT hellip; INTO hellip; statement is executed in PL_ SQL, if the returned result set is null, The NO_DATA_FOUND error i

When designing a table, we sometimes argue about whether the field allows null values. The database master Kalen Delaney gave me some suggestions. 1. Never allow null values in the User table 2. the user table definition contains a not null limit. 3. Do not rely on Database properties to control null values. For th