Tag:Field name

  • Fastjson initial lowercase problem solving


    Welcome to my blogerror0 BlogThe code is copied directly. The format is messy. Let’s make do and have a look If you want to keep the fields as they are, fastjson defaults to getting the fields of the get method and converting the initial letter to lowercase. Solution: 1. Add instantiation configuration Json.tojsonstring (the object […]

  • MySQL combines multiple rows of results into one row with commas


    explain: 1.GROUP_ The value in concat () is the field name of the data you want to merge;  The separator function is used to separate the data to be merged. It is separated by commas by default;  ’is the symbol you want to use to separate; 2. Group by statement must be used for group […]

  • MySQL data definition language (DDL)


    Write in front In this paper[content]On behalf of ah, optional, you can write or not. Introduction to the basic functions of SQL language SQL is a structured query language with the following functions: Data definition language (DDL): full name: data definition language Data manipulation language (DML): full name: data manipulation language Data query language (DQL): […]

  • Let’s talk about the time attributes of the flick table


    order This paper mainly studies the time attributes of the flick table Processing time Defined by fromdatastream DataStream<Tuple2<String, String>> stream = …; // declare an additional logical field as a processing time attribute Table table = tEnv.fromDataStream(stream, “Username, Data, UserActionTime.proctime”); WindowedTable windowedTable = table.window(Tumble.over(“10.minutes”).on(“UserActionTime”).as(“userActionWindow”)); If you create a table from a datastream, you can define […]

  • Talk about the definition of Flink table schema


    order This paper mainly studies the definition of the Flink table schema example Define fields and types .withSchema( new Schema() .field(“MyField1”, Types.INT) // required: specify the fields of the table (in this order) .field(“MyField2”, Types.STRING) .field(“MyField3”, Types.BOOLEAN) ) Define field name and field type through field Define field properties .withSchema( new Schema() .field(“MyField1”, Types.SQL_TIMESTAMP) .proctime() […]

  • Sqlserver queries the column name, description, remarks, comments and types of a table or library


    Comments on tables or table fields are extended attributes of database objects. In MSSQL, some annotative contents can be put into the database or database objects to enhance readability and contribute to future management and maintenance. The contents of extended attributes can be added, modified or deleted through SSMS, queried through system view, and maintained […]

  • Data processing of database import and export


    Background: I’ve been doing back-end development recently. Often encountered is the import and export of database data. Here is a detailed record of the steps of importing and exporting through graphical tools.Tools: Excel, SQL Server graphical tools. Put a picture of fat tiger first! Import Excel data from database (1) First process the excel header […]

  • Don’t even know what happens if you don’t tag a JSON package variable? Young man’s tail juice


    problem jsonWhen used in the package, the variables in the structure are not addedtagCan it turn into normaljsonThe fields in? How to answer If variableInitial lowercase, thenprivate。 in any caseCan’t turn, because you can’t get itReflection information。 If variabletitle case, thenpublic。 No tagCan be converted tojsonFields in the,jsonThe inner field name is the same as […]

  • HBase + Phoenix + mybatis + springboot integrate query data


    Phoenix query server provides an alternative way to interact with Phoenix and HBase. Soon, this will allow access from an environment other than the JVM. In versions 4. X and 5.0, the query server and its JDBC client are part of the standard Phoenix distribution. They do not require other dependencies. After version 5.0, the […]

  • MySQL operation existing table (alter table)


    explain: The content in < > is self defined The contents in [] can be omitted Field contains the field name and data type_ Name only refers to the field name table_ Name refers to the name of the table Position refers to the position of the field, and the values can be: first, after […]

  • Mybatis use Oracle to add data


      This time, the blogger mainly develops Oracle database. For a long time, he didn’t use Oracle, and he has forgotten many knowledge points. This time, he mainly reviews some SQL statements used in his work; query All query statements are normal, but it should be noted that when querying Oracle database, when using alias for […]

  • Hive window function


    Window functions are supported in hive, and MySQL is also supported after version 8.0. It’s like opening and hanging after using it! Window function is also called window function and analysis function. The aggregation function can aggregate multiple rows of data into one row according to regulations. Generally speaking, the number of rows after aggregation […]