The following is the previous school that time do notes, not well organized, make do with it, or very useful to the novice
The select logo to choose which columns. The from logos in the table from which to choose. As column alias can be omitted, alias to use double quotation marks, can contain Spaces or special characters in the nickname and case-sensitive. | | the column and column, column joins in the character select ename | | ‘_’ | | job as “Employees” from emp; Date and character string can only appear in single quotation marks the select ename | | ‘is a’ | | job as “the Employee Details” from emp; Select distinct deptno from emp;
SQL: a language ANSI standard keywords cannot be abbreviated Use statements to control table definition information and data in a database SQL * PULs an environment one of the features of Oracle keywords can be abbreviated commands cannot change data values in a database run centrally
Desc Displays the table structure
Select empno,ename,job,deptno from emp where deptno=10; select empno,ename,job,deptno from emp where deptno=10;
The characters and dates must be enclosed in single quotation marks. The characters are case-sensitive and the date format is sensitive. The default date format is DD-mon-rr.
Comparison operator
Operator = > >= > <= <> Meaning Greater than or equal to greater than or equal to less than or equal to not equal to (can also be! =)
Assignment uses :=