Last updated: 2020-12-22 10:44:53

    Overview

    This command is used to learn about command usage.

    Syntax

    ## Obtaining All Commands and Their Usage
    help;
    
    ## Obtaining the Detailed Instruction of a Specific Command
    help [command];

    Sample

    tcaplus> help;
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          help: show usage of commands, example: "help select;".
          show: get server status related information. executing "help show;" for details.
          exit/quit: exit the client.
         count: print record number in the database.
    
          desc: print table field name and type.
        select: query records from database.
        insert: insert a new record into database.
       replace: replace a record into the database.
        update: update a record in the database.
        delete: delete record(s) from database.
    
          dump: dump records from database.
          load: load records into the database.
    
        setttl: set ttl for a record
        getttl: get ttl for a record
    
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    tcaplus> help select;
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    example: select key1, key2, key3, value1, value2 [into result.csv] from table where key1 = 1 and key2 = "abc" [and -index = 1] [\P] [\G];
             query records from database, you can specify part of the fields or whole fields (select *), and you can write the result to a file, which can be used by "insert" and "load"
             for generic table, if the key in where clause is not complete, then it will send "GetByPartkey"
             for list table, if "-index" is not specified in where clause, then it will send "ListGetAll", otherwise it will send "ListGet"
             \P: print time usage in detail
             \G: print fields in column
             Note: "-index" only used for list table
    
    example: select * [into result.xml] from table where key1 = 1 and key2 = "abc" [and -index = 1] using tdr [\P];
             if you specify "using tdr", then the records will be parsed by tdr file and print in xml format. you can write the result into a file, which can be used by "load"
             it only support "select *" instead of select part of the fields when specify "using tdr"
             Note: "-index" only used for list table
    
    globle index query:
       example: select * from table where key1 > 1 and value1 > 100;
       example: select * from table where value1 like "test";
       example: select field1, field2 from table where key1 > 1 or value1 > 100;
       example: select * from table where value1 between 100 and 200;
       example: select * from table where value1 > 100 limit 100 offset 0;
       example: select sum(value2), max(value2), min(value2), avg(value2), count(*) from table where value1 > 100;
       Note: globle index query is only support generic table;
       Note: current support: =,!=,>,>=,<,<=, like, not like, betwwen, in, not in, and, or, limit offset;
       Note: current support aggregation: count, sum, max, min, avg;
       Note: for protobuf table, it support: "select field1.field2 from test where value1 > 100";
       Note: limit must be used with offset, lack offset will query failed;
       Note: the fields in where condition and in aggregation must had already created index;
       Note: it not support: store the result to a file, such as "select * into file XXX" is not support;
       Note: it not support: "select * from table"; which means to traverse table, you can used api traverse method to traverse table;
       Note: it not support: order by, group by, having, join, union and so on;
       Note: it not support: select a+b XXX; select * from table where a+b>0; select sum(XX),field1 from XXX; select *,field1 from XXX; ......;
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