sql basics pdf

table has a value, and no match is substituted with a null value.SELECT * from A left OUTER JOIN B on a.name = B.nameA 3.RIGHT [OUTER] JOIN produces a full set of Table B, and a match in table A has a value, and no match is substituted with a null value.SELECT * from A right OUTER JOIN B on a.name = B.nameThe 4.FULL [OUTER] JOIN produces a and B's set. For records that do not have a match, NULL is the value.SELECT * from A full OUTER JOIN B on a.name = B.nameYou can find the value without match

) from EMP;Select Job,avg (SAL) from EMP*ERROR at line 1:Ora-00937:not a single-group group function--Use the HAVING clause to filter the grouped results-Query The department number above the average wage and its average wage.Select Deptno,avg (SAL) from EMP Group BY DEPTNO have avg (SAL) >2000;Idle> Select Deptno,avg (SAL) from EMP Group BY DEPTNO have avg (SAL) >2000; DEPTNO AVG (SAL)--------------------20 217510 2916.66667　　--to find out the average wage in the above jobs (job)Select Job

8. Calculated fieldsConcat () Splicing stringMysql> SelectConcat (Name,'-', msg) fromPw_luck;+-----------------------+|Concat (Name,'-', msg)|+-----------------------+|Wilson- - ||Zhangsan- - ||Lisi-1001 ||Wang5-1001 ||Zhangsan7- + ||Zhangsan8- + ||Zhangsan9- + ||Wang5- + ||Wang5%- - ||WANG5- + |+-----------------------+TenRowsinch Set(0.00SecRTrim () Remove right space LTrim () remove left space Trim

Tags: def modify pre number not block PAC creat time1. How the data is stored (table property Operations) 1.1 questions to consider before building a table A. Table name B. table contains data type (CHAR (fixed-length character), VARCHAR (indefinite long character), number (numeric), date (date and time), BLOB (large data set), straight string, custom type) C. Fields that make up the primary key D. length of each field E. Which fields can be null1.2 CREATE TABLE Statement Ba

Label:16 inserting INSERT into table values ()Mysql> Insert intoPw_priceValues(5, the,'Cai'); Query OK,1Row affected (0.03sec) MySQL> Select * fromPw_price;+-----+-------+------------+|Uid|Price|First_Name|+-----+-------+------------+| 1 | - |Wang|| 2 | + |Zhang|| 3 | - |Li|| 4 | the |Weizhi|| 5 | the |Cai|+-----+-------+------------+5Rowsinch Set(0.00SecInsert a partial fieldMysql> Insert intoPw_price (Uid,first_name)Values(6,'Guo'); Query OK,1Row affected (0.03sec) MySQ

A1. 1 LTRIM (character_expression)-- Delete the starting space in the character variable 2 RTRIM ( character_expression)-- Delete trailing spaces in the character variable 2. Gets the start position of the returned start of the specified string. Return position starting from 1, not starting from 0 1 CHARINDEX (expression1, expression2 [ , Start_location ] ) (ii) SUBSTRING (expression, start, length) parameter expression is a string, a binary string, a text, an image, a column, or a containing

Straight to the point------F41. EnquirySearch queries for the specified data table or view to find the functionality that meets the query criteria, including the following SQL syntax, where "" is optionalselect2. Defining the DDLData definition Language, a language used to define and revoke a specified database object (data tables, views, indexes, stored procedures, users, etc.),①. The "Create table/alter table/drop table" statement for the data table

(commit statement)Committing a transaction means persisting all the operations of the database to the database, which is usually done using a commit statement. Execution order:A. Records that the current transaction has been committed within the rollback segment and claims a unique system number (SCN) to uniquely identify the transaction. B. Start the background log write process (LGWR), write the data in the redo log buffer of the SGA area and the SCN of the current transaction into the redo