teradata sql queries

Overview and terminology In MicrosoftSQL Server 2000, distributed queries allow SQL Server users to access data other than SQL Server based servers (in other servers running SQL Server or in other data sources with OLE DB interfaces). OLE DB provides a unified way to access list data from heterogeneous data sources.

13.2. Named SQL queries Named SQL queries may be defined in the mapping document and called in exactly the same way as a named hql query. In this case, we doNotNeed to callAddentity (). SELECT person.NAME AS {person.Name}, person.AGE AS {person.Age}, person.SEX AS {person.Sex} FROM PERSON

can automatically optimize queries based on the where clause, it is still necessary for you to understand the working principle of the "query optimizer". If not, sometimes the query optimizer does not perform quick queries according to your intention.In the query and analysis phase, the query optimizer checks each stage of the query and determines whether the data volume to be scanned is useful. If a phase

: Sum as long as all with distinct two count specification, none *.Calculate the sum of students ' ages:SELECT SUM (Student_age) from T_student;returns the column average ( AVG ):Calculate the average age of students:SELECT AVG (Student_age) from T_student;returns the maximum value / Minimum Value ( Max/min ):Ask for the oldest student information (minimum value same):SELECT MAX (Student_age) from T_student;Note: You can only find the maximum age, to show the oldest students all information,

to load the corresponding object of a record.Customer customer = (customer) session.get (customer.class,1);Customer customer = (customer) session.load (customer.class,1);3. Hql Search methodHQL (Hibernate query Language) is an object-oriented query language that is somewhat similar to the SQL query language. Among the various retrieval methods provided by Hibernate, HQL is the most widely used method of retrieval. It has the following features:Set va

This blog post provides a brief introduction to several types of queries commonly used in SQL Server and how to use them.First, ExecuteScalar method gets a single value The ExecuteScalar method is one of the methods of the SqlCommand class, executes the query, and returns the first column in the first row of the result set returned by the query. Class Program {static void Main (string[] args) {string st

30 common methods for optimizing SQL statement queries in MySQL, bitsCN. com1. to optimize the query, try to avoid full table scanning. First, consider creating an index on the columns involved in where and order. 2. try to avoid using it in the where clause! = Or 3. try to avoid null value determination on the field in the where clause. Otherwise, the engine will discard the index and perform full table

SQL Server queries 31 to 40 records in the table, and writes an SQL statement to output 31 to 40 records in the UserInfo table in case of discontinuous IDS (the database is SQL Server, and the Automatically increasing id is used as the primary key, note that the ID may not be consecutive )? According to the meaning of

Tags: mysql optimized sql slow logRecently, a development team complained that our platform contains MySQL cluster not, always reported the MySQL "Heartbeat Error", analyzed the logs they collected, did not find the network between the MySQL cluster node problem, but found a very interesting phenomenon , in the MySQL slow log found a large number of slow queries, basically is more than 1 seconds, it is obvi

, if not added distinct the result is the number of table rows--5.returns the column total value (SUM):Note: Sum as long as all with distinct two count specification, none *. Calculate the sum of students ' ages:SELECT SUM (student_age) from T_student;Return column average (AVG):Calculate the average age of students:SELECT AVG (student_age) from T_student;Returns the maximum/minimum value (max/min):Ask for the oldest student information (minimum value same):SELECT MAX (student_age) from T_studen

SQL Server queries all users who have purchased products in a certain period of time, and SQL server has bought The goods table is as follows: Name time productA 13:23:00 WFEYB 15:23:00; 34 ASGA 13:47:20 SGHC 19:56:03 HRTC 14:00:00 XCCA ESFW Select distinct oo. name FROM (SELECT name, DATE_FORMAT (time, '% h: % m') AS ti FROM goods) as oo where ti BETWEEN '12:

SQL Server queries all Sundays within a period of time, and SQL Sunday /* Query all Sundays within a period of time @ startdate start date @ enddate end date */declare @ startDate datetimedeclare @ endDate datetimedeclare @ week varchar (20) set @ startDate = '000000' set @ endDate = '000000' while @ startDate Copyright Disclaimer: This article is an origina

Select column_id, column_name, parent_id, (select column_name from [sort] Where column_id = A. parent_id) parent_name,(Select parent_id from [sort] Where column_id = A. parent_id) fathers_id,(Select column_name from [sort] Where column_id = (select parent_id from [sort] Where column_id = A. parent_id) father_nameFrom [sort] A where column_depth = 3 order by father_name DESC, parent_name DESC, column_name DESC Compared with SQL statements of niub,

Several friends have such questions: select * from tab1, tab2 where tab1.id = tab2.id and tab1.col1 = 123 and tab2.col1 = 'abc' According to the execution order you described, tab1 and tab2 are first given the Cartesian product, and then filtered by tab1.col1 = 123 and tab2.col1 = 'abc. In this case, the efficiency is not very low. Is the database so stupid?I think many people will have this question, including the question I raised when I first studied. In this article, I will

;string sql = "SELECT * from user where username=?" and passwd=? "; PS = conn. PreparedStatement (SQL);p s.setstring (1, "admin");p s.setstring (2, "123456"); ResultSet = Ps.executequery (); Specific implementation Code reference java PreparedStatement (Java Platform SE 7) nbsp, other languages can be implemented against his principles. Parameter queries are the

When the analyzer looks for a path, it does not count the number of rows and ranges of values contained in the index every time, instead, the information is created and updated based on certain conditions and saved to the database. This is the so-called statistical information. How to view statisticsIt is very simple to view SQL Server statistics. Run the following command:DBCC SHOW_STATISTICS ('table name', 'index name ') The result 1 is displayed.

In general Server databases operate in a single thread when performing query jobs. SQL Server provides the parallel query function to cope with large-volume query tasks. The advantage of parallel query is that it can process query jobs through multiple threads, thus improving the query efficiency. SQLThe server database provides the parallel query function for database servers with multiple CPUs to optimize the performance of query jobs. That is to s

SQL Server blocks access to the statement 'openrowset/OpenDataSource 'of the 'ad hoc distributed queries' component because this component has been disabled as part of the server's security configuration. The system administrator can enable 'ad hoc distributed queries 'by using sp_configure '. For more information about enabling 'ad hoc distributed querys', see "

Recursive queries in SQL statements SqlServer2005 and Oracle two versions Before using Oracle, think of its recursive query is very useful, the study of SQL Server, found that it also supports recursive query in SQLTo illustrate:The SqlServer2005 version of SQL is as follows:For example, a table with ID an

for queries. SQL queries are optimized based on the data in the table. When there is a large number of duplicate data in the index column, SQL queries may not use indexes, for example, if a table contains sex fields, male and female are almost half of each other, indexing s