if statement in select query

Label:Common select various query formats:General Query1. Select * FROM table name2. Select * FROM table name where column name + conditionInternal connection3. Select column name, column name from table name 1 inner JOIN table name 1 on table Name 2. column name = table Nam

Advanced query technology is mainly related to multiple tables linked query technology, embedded SELECT statement subquery technology, the combination of multiple queries combined technology. 1. Connection Query You need to retrieve data from two or more tables at the same

statement conforms to the syntax definition, the server process then checks the fields, tables, and so on in the statement. Look at the fields and whether the tables are in the database. If the table name and column name are inaccurate, the database will feed back the error message to the client.So, sometimes when we write the SELECT

Database systems are the core of management information systems and one of the most important computer applications. From the perspective of most system application instances, query operations account for the largest proportion of various database operations. Let's take a closer look at the common query statements in queries-select statements! This is the genera

Tags: Oracle where generalSQL query statement describes the--select statement1. Simple SELECT query statement1.1 Check.Sql> select * from EMP;1.2 Check ListSql> select Empno,ename from

Tags: blog http ar using SP for strong on data1. Single-Table query: Filter the records in the table according to where conditions, form an intermediate table (this intermediate table is not visible to the user), and then select the corresponding column according to the Select column of select to return the final resul

1. Query the SELECT query statement execution plan using explainMysql> select * from baba where name = ' FJDSJF ';+------+--------+| ID | name |+------+--------+| 1 | FJDSJF |+------+--------+Query the execution plan for the SQL s

, Atitle, PIDNumber name superior number for province and municipality PID is nullIn this way we want to correlate the query to the subordinate data, need to use the self-correlation. To Create a table:CREATE table area (Aid int PRIMARY KEY,--own numberatitle varchar (20),--Own namePID INT--The number of the superior );Self-correlating statements:Select City.* from area as CityINNER join area as provinceOn city.pid = province.id;where province.

menMysql> Select COUNT (*) from student where gender= "male";15. Find Max Max ()Mysql> select Max (score) highest score from student;16. Find min min ()Mysql> Select min (score) highest score from student;17, sub-queryMysql> SELECT * FROM student where score= (select Max (s

How do I retrieve the result set of a stored procedure (store Procedure) in a SQL Server query statement (Select)? (2006-12-14 09:25:36)Other descriptions of the same nature as this issue include:How do I get an execution result recordset for another stored procedure in a SQL Server stored procedure?How do I retrieve the execution results of a dynamic SQL

If we now use a SELECT statement to query data from a database, how does the Oracle database work? What can we learn from it? Below, combine a simple SELECT statement to see the operating mechanism of Oracle database backstage. This is very helpful for our subsequent system

| | 9 | NingZhongze | F | 49 | + ----- + -------------- + -------- + ------ + 9 rows in set (0.00 sec) This is the data used in the following example. You can refer to it first; The first is the mysql query statement: Query category: Single Table query: simple query Mul

MySQL uses the select statement to query the data of the specified column (field) in the specified table. This article describes how to execute a select query statement in the MySQL database to

In VFP, you can use SQL statements to manipulate tables, and you do not need to open the database when you use SQL statements to manipulate tables. This example describes the Select query statement (data retrieval), and the format of the SELECT statement refer to the

MySQL Query statistics per select statement MySQL Query statistics per select statement Where can I use a single select statement to implem

Tags: MySQL query statement select explain and practiceSelect statement execution Process:START ———— >from------>where (SELECT, appropriate line)--------->group by (grouping)---------->having (filtering the grouping) ———— >order by ( Sort) ———— >

Example of a Select query statement in Php To query the content in the mysql database in php, we must first connect to the mysql database and then use the SQL statement for query. Let's take a look at some examples below. SQL has

viii. Query Statement select for hive In all database systems, the SELECT statement is the most used, but also the most complex piece, the query in hive Select support syntax is certai

Mysql paging query is a common problem. How can this problem be achieved? The following describes how to implement mysql paging query. Mysql paging query is a common problem. How can this problem be achieved? The following describes how to implement mysql paging query. Using a feature of the

MySQL query statistics for a single SELECT statement is often complex in writing statements. The following describes how to use only one SELECT statement to help you. Where can I use a single SELECT