EXPLAINformat=TRADITIONALjsonSELECTtt.TicketNumber,tt.TimeIn,tt.ProjectReference,tt.EstimatedShipDate,tt.ActualShipDate,tt.ClientID,tt.ServiceCodes,tt.RepetitiveID,tt.CurrentProcess,tt.CurrentDPPerson,tt.RecordVolume,tt.DPPrinted,et.COUNTRY,et_1.COUNTRY,do.CUSTNAMEFROMtt,et,etASet_1,doWHEREtt.Subm...
圆脚框--group/sort,分组或排序 钻石框--joins Framed boxes(有外框)--子查询。 Join type连接类型: https://dev.mysql.com/doc/refman/8.0/en/explain-output.html#explain-join-types 力扣550例子 CreatetableIfNotExistsActivity (player_idint, device_idint, event_date date, games_playedint)Truncatetab...
This tableis referenced as the child of table in a join that can be pushed down to the NDBkernel. Applies only in MySQL Cluster, when pushed-down joins are enabled. Seethe description of the ndb_join_pushdown serversystem variable for more information and examples. const row not found (JSON...
EXPLAIN returnsa row of information for each table used in the SELECT statement. It lists thetables in the output in the order that MySQL would read them while processingthe statement. MySQL resolves all joins using a nested-loop join method. Thismeans that MySQL reads a row from the first ...
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We recommend that you prevent non-equivalent joins in SQL statements. The following code provides an example of a nested loop join. BEGIN; CREATE TABLE public.nestedloop_test_1 ( a integer not null, b integer not null ); CALL set_table_property('public.nestedloop_test_1', 'distribution_...
Example 2: Analyzing Joins Consider a query joining employees and departments tables to retrieve department names along with employee data. Code:> -- Analyze the join performance between employees and departmentsEXPLAINANALYZESELECTe.id,e.name,d.department_nameFROMemployees eJOINdepartments dONe.departmen...
The main IndexJoin thread joins each outer row by looking up to the inner rows' hash table. The IndexJoin operator contains the following execution information: inner:{total:4.297515932s, concurrency:5, task:17, construct:97.96291ms, fetch:4.164310088s, build:35.219574ms}, ...
By default,DESCRIBEdisplays information about all columns in the table.col_name, if given, is the name of a column in the table. In this case, the statement displays information only for the named column.wild, if given, is a pattern string. It can contain the SQL%and_wildcard characters...
It makes these decisions based on the statistical information it has about your data and by leveraging Oracle database features such as hash joins, parallel query, partitioning, etc. Still it is expected that the optimizer will generate sub-optimal plans for some SQL statements now and then. ...