select count distinct

Http://www.taobaodba.com/html/851_sql%E4%BC%98%E5%8C%96%E7%9A%84%E4%B8%80%E4%BA%9B%E6%80%BB%E7%BB%93.html SQL optimization is an indispensable part of the DBA's daily work, remember in the student period, once saw a post on the itpub, when the

SQL Server Databasethe Count () function returns the number of rows that match the specified criteria. The syntax SQL count (column_name) syntax count (column_name) function returns the number of values for the specified column (NULL does not count

Article Source: http://www.ynpxrz.com/n822738c2024.aspxT_tudent (sid,sname,sage,ssex,sdept) Student tableT_course (Cid,cname,tid) timetableT_score (scid,sid,cid,grade) score tableT_teacher (tid,tname) Teacher tableProblem:1, the inquiry "001" course

Http://www.ynpxrz.com/n822738c2024.aspxT_tudent (sid,sname,sage,ssex,sdept) Student tableT_course (Cid,cname,tid) timetableT_score (scid,sid,cid,grade) score tableT_teacher (tid,tname) Teacher tableProblem:1, the inquiry "001" course is higher than "

1. Clustering factor algorithm:Locate the block number that corresponds to the record by Dbms_rowid.rowid_block_number (ROWID). rowID is recorded in the index, so Oracle can determine whether the record is in the same block based on the ROWID in the

This article consists of @lonelyrains produced. Reprint please indicate the source. article Links: http://blog.csdn.net/lonelyrains/article/details/44225533Previous article for the bug statistical analysis of the preliminaryThis article focuses

Student (s#,sname,sage,ssex) Student tableCourse (c#,cname,t#) timetableSC (s#,c#,score) score tableTeacher (t#,tname) Teacher tableProblem:1, the inquiry "001" course is higher than "002" of all students of the school number;Select a.s#From (select

One, why do you want to open this query?The database is a very easy place to create bottlenecks, and now nosql people are talking about the heat, and it's estimated that the database is depressing. MySQL is the most affected by the speed of the

public void GetData (string username, string Userip, String UserKey, String Userareaid, String ypid, String In_prov Inces, String Yearid, out DataTable data, out string out_success, out string out_message) {try {String constr =

First, what is the waterline (high water Mark)?All Oracle segments (segments, where, for ease of understanding, suggest segment as a synonym for a table) have a limit on the amount of data that can be accommodated in a paragraph, we call this cap

The database engine uses indexes to improve query efficiency and adds many optimization policies for indexes. However, there are also many details during the indexing process. If you ignore these problems, hard-built indexes may not be well applied,

Today, my friend asked a particularly tangled question: in a database table, we need to repeat a field in the table and sort the remaining data by another field, Today, my friend asked a particularly tangled question: in a database table, we need to

I. Data Table Student (S #, Sname, Sage, Ssex) Student table S #: Student ID; Sname: Student name; Sage: Student age; Ssex: Student gender Course (C #, cname, T #) curriculum C #, course number; Cname: Course name; T #: Instructor id SC (S #, C #,

This text has been reprinted online, and some SQL statements are suitable for use in application systems. Some "reports" have a heavier feeling, mainly to review the former. This text has been reprinted online, and some SQL statements are suitable

Oracle archive data query (partition query) the SQL statement used to query 201212 month data records is as follows: SQL code www.2cto.com SELECT COUNT (DISTINCT (c. caller_nbr) AS emp_use_count FROM tab_pub_calllog c WHERE TO_CHAR (c. end_time,

Today we found that indexes are not used in an SQL query, and classid is used to create indexes, as shown in the following figure: select * frominfobasewhereclassidin (10001,10002, 10003,10 Today we found that indexes are not used in an SQL query.

Mysql year/year grouping statement Java code SELECT count (DISTINCT (. rect_id) zcount,. job_dept, DATE_FORMAT (submit_date, '% Y-% m') zsubmit_date FROM table name a WHERE. statu = 3 AND. rstatu = 2 AND. job_dept IN ('19', '20', '21') group by. job_

SyntaxUse CAST: CAST (expression AS data_type) Use CONVERT: CONVERT (data_type [(length)], expression [, style]) ParametersExpression Is any valid Microsoft SQL Server "expression. For more information, see expressions. Data_type The data types

Copy codeThe Code is as follows:-- Basic SQL operations -- Create a database Create database Studets -- Create a table Create table student (sno char (5), sname char (20), ssex char (2), sage smallint, sdept char (15 )) Create table course (cno char

Detailed description of oracle high water level line and oracle water level line 1. What is a High Water Mark )? All the oracle segments (segments here, for ease of understanding, we recommend that you use segment as a synonym for the table) have an