Statement:语句,通常指整个SQL文本 Clause:子句,通常指SQL文本中的一部分,如From子句、Where子句、Group By子句 Query:查询,通常指SQL文本在系统中的一次执行实例 Database:库,一个库可以有多个表;含义类似的有:模式(Schema) Table:表,一个表可以有很多行;含义类似的有:关系(Relation) Row:行,一行可以有很多列;...
NOTE: SQL commands are not case sensitive. The above SELECT statement can also be written as"select first_name from students_details;" You can also retrieve data from more than one column. For example, to select first name and last name of all the students. ...
switch的条件可以时变量也可以是表达式,数值类型为byte、char、short、int、enum枚举、String字符串。 case后的值只能是常量,不能是变量,也不允许重复。 default后是找不到对应的case值时默认执行的语句。default的break完全可以省略,没有任何影响。case后的break也可以省略,省略后会继续往下执行下一个case的语句体(ca...
The SELECT statement inSQLisused to retrieve rows from a database table. It lets you specify which columns of the table to fetch and the criteria for rows. The data returned is called a result set and is displayed in your development tool or used by the application that ran the query. ...
TheSELECTstatement is used to select data from a database. ExampleGet your own SQL Server Return data from the Customers table: SELECTCustomerName, CityFROMCustomers; Try it Yourself » Syntax SELECTcolumn1,column2, ... FROMtable_name; ...
3. Types of CASE Statements There are two main types of CASE statements in SQL: simple CASE searched CASE They differ in how they compare values or evaluate conditions. 3.1. Simple CASE To begin with,a simple CASE statement compares an expression to one or more possible values. It has a ...
Answer: C.SQL statements are not case sensitive. Column Heading Defaults: 默认的列标题(表的第一行): Arithmetic expressionsandNULLvalues in theSELECTstatement SELECT语句中的算术表达式和空值 首先介绍显示表结构的命令 DESCRIBEcommand 描述命令:显示表结构 ...
#这个时候Sql_cmd_dml::execute_inner函数也执行完成了,进而Sql_cmd_dml::execute,mysql_execute_command也接着执行完成 #执行到dispatch_command函数的thd->send_statement_status(); 这一行,看到客户端执行的查询语句也输出了结果 #执行到handle_connection的while (thd_connection_alive(thd)) {if(do_command(...
This tutorial shows you how to use the PL/SQL SELECT INTO statement to fetch data of a single row from a table into variables.
13.2.9 SELECT Statement SELECT[ALL|DISTINCT|DISTINCTROW][HIGH_PRIORITY][STRAIGHT_JOIN][SQL_SMALL_RESULT][SQL_BIG_RESULT][SQL_BUFFER_RESULT][SQL_CACHE|SQL_NO_CACHE][SQL_CALC_FOUND_ROWS]select_expr[,select_expr]...[into_option][FROMtable_references[PARTITIONpartition_list]][WHEREwhere_condition...