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v4.0
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    v4.0

      coalesce() | Coalesce (V4.1)

       V4.1 

      Parameters, Value

      Coalesce function merges multiple (≥2) columns into one column, it keeps the first non-null value in each row and disgards the rest of the values. If any row contains only null values and there is no <constant> parameters, then that row results in null ultimately.

      if columns are not homologous: when used in WITH, table() will first make a Cartesian Product Combination of all columns and its homologous columns before merging; when used in RETURN, table() will trim all columns and their homologous columns before merging.

      Syntax:

      • Format: coalesce(<column1>, <column2>, ..., <constant>)
      • Parameters: see table below
      • Value: ATTR
      Name Category Specification Description
      <column> ATTR / The column to be merged
      <constant> ATTR Not mandatory Non- null constant; if all values of a column of data are null,then merge the data from that column and take the value of the constant

      Alias (Homologous)

      Example: find 10 cards, return the time of opening cards; return the expiry time if the opening time is null

      find().nodes({@card}) as n
      limit 10
      return coalesce(n.open_date, n.expire_date) 
      

      Example: find 10 cards, return the time of opening cards; return the expiry time if the opening time is null; return 0 when the expiry time is null

      find().nodes({@card}) as n
      limit 10
      return coalesce(n.open_date, n.expire_date, 0) 
      

      WITH Alias (Non-homologous)

      Example:

      uncollect [1,2,3] as a1
      uncollect [4,5] as a2
      with coalesce(a1, a2) as a3
      return a3
      

      RETURN Alias (Non-homologous)

      Example:

      uncollect [1,2,3] as a1
      uncollect [4,5] as a2
      return coalesce(a1, a2)
      
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