day 05 DQL data query language --- connection query --- enter the room

Because sql statements are not case sensitive, all commands in this article use lowercase for convenience Previous contents day 01 first knowledge of Mysql and DDL data definition languageday 02 DML data operation languageday 03 DQL data query language -- a first glimpseday 04 DQL data query language - single table query - a slight succ ...

Posted by kampbell411 on Tue, 29 Mar 2022 07:33:25 +0300

Database computer experiment 3 (cursor)

For database Experiments 1 and 2 and database creation, please Refer here What is a cursor? Cursor is a data buffer set up by the system for users to store the execution results of SQL statements. Each cursor area has a name. Users can use SQL statements to obtain records from the cursor one by one, assign them to the main variable, and submit ...

Posted by Reef on Tue, 29 Mar 2022 02:46:55 +0300

oracle quick start Chapter 6 triggers & built-in packages

1: Trigger 1. Key words of trigger: trigger 2. Overview: it is a special stored procedure, and the stored procedure is a special function When the DML (data manipulation language) statement is executed, the trigger will be triggered and executed automatically, rather than requiring manual call like a function. 3. Syntax of trigger: create ...

Posted by headmine on Sun, 27 Mar 2022 09:15:10 +0300

Creation and management practice of SQL basic data table

Experimental reportexperimentRead data table 1-table 4 and consider whether it is reasonable to add constraints to each fieldWrite T-SQL statements, create tables and constraintsView information about creating tablesVerify data integrity by inserting data into the table and answer the appropriate questionsExperimental task 1Using T-SQL to compl ...

Posted by Exemption on Sat, 26 Mar 2022 22:05:12 +0300

Get historical execution plan: AWR/StatsPack SQL Report

Get historical execution plan: AWR/StatsPack SQL Report When a SQL performance problem occurs, you may want to look at the historical execution status to confirm whether there is any change. In this case, Oralcle's AWR/StatsPack SQL report is very useful. AWR SQL Report The information obtained by the AWR (Automatic Workload Repository) ...

Posted by samafua on Sat, 26 Mar 2022 17:25:56 +0300

Detailed and complete knowledge of sql statements

Modify database table Modify table name: alter table Old table name rename as New table name Add table fields alter table Table name add Field column properties For example: alter table student age int(11) Modify the fields of the table Modify constraints alter table Table name modify Field column properties[]; For example: ...

Posted by jyushinx on Sat, 26 Mar 2022 12:26:12 +0300

Use Python to dynamically generate SQL statements for creating tables (using Pandas Library) according to the attribute table excel file of a specific format

Problem description There are 33 national standard attribute table excel files, and the database table needs to be built according to these standard attribute tables. The format of each excel is as follows: For such heavy and basically brainless work, I choose Python to do it: code import pandas import re def getStandardDataType(x): ...

Posted by LiamOReilly on Sat, 26 Mar 2022 06:52:41 +0300