The value of distinct is displayed only once. However, this value is displayed only once. Select distinct field name 1, field name 2 from Table order by field name 1 distinct field name 1 means that only one field name 1 is displayed for the first time. It is best to use it in combination with order. Efficiency can be improved. Note that distinct returns a unique result set. It is a result set. If you select n fields, it will be regarded as phase only when n fields are the same... related discussion [question] How to Use distin in hql...
Select U. firstname, U. lastname, U. Email, U. createdby from user u, u. personas P where P. isclient =?
Order by U. the hql statement lastname contains repeated records in the email. I want to remove the duplicate records in the result, so I added a distinct and changed it to select...Processing of large fields in a data table
Large field types are often used in databases, such as long/BLOB/clob in Oracle, text/image in sqlserver, and text/longtext/clob/BLOB in MySQL. There are two types of stored information: long text, such as large text segments. A common varchar can only store up to 4000 Chinese characters and cannot meet the requirements; the other is to store binary information, such as uploaded files. Now let's assume there is a table that records the text published by someone... hql.
If the program is well written, it depends on how the code is written. Take a closer look at the following two hql statements. What is the difference: 1. From sinoasndetail A where a. asn. Warehouse =: warehouse and A. asn. receivedtime >=: begintime and A. asn. receivedtime <=: endtime and A. I...Oracle SQL and SQL * Plus Learning (...
Oracle SQL And SQL * Plus Learning (on) (14:21:10) tags: Literature/originality
1. Select Row 1. Simple SELECT statement select [distinct] {*, column [alias],… ...SQL Problems
Select distinct G. * from groups G Inner join topics t on (T. group_id = G. ID) order by T. created_at DESC limit why is the result incorrect? Compared with select
G. * from groups G Inner join topics t on (t...The related blog D distinct only displays a larger value for one replay. No matter how many times this value appears, it is only displayed once. Select distinct field name 1, field name 2 from Table order by field name 1 is best used with order. It can improve efficiency. Distinct sorts the returned result sets, which greatly affects the query efficiency. When the first N records of non-repeat records are retrieved, distinct will affect the rownum constraint bar. No matter how many times this value appears, it is only displayed once. Select distinct field name 1, field name 2 from Table order by field name 1 is best used with order. It can improve efficiency. Distinct sorts the returned result sets, which greatly affects the query efficiency. When the first N records of non-Repeated Records are retrieved, distinct will affect the deduplication of rownum... Oracle, without distin...
The distinct keyword can only be used to filter all records in the query field that are the same (the record set is the same). If you want to specify a field, it does not work. In addition, the distinct keyword is sorted, Which is inefficient. Select distinct name from T1 can eliminate duplicate records, but only one field can be taken. Now, the value of ID and name must be taken at the same time. Select distinct ID, name from T1 can take multiple fields, but only the two fields with the same values can be eliminated... Oracle SQL and SQL * Plus Learning (...
Oracle SQL And SQL * Plus Learning (on) (14:21:10) tags: Literature/originality
1. Select Row 1. Simple SELECT statement select [distinct] {*, column [alias],… ...
